I don't have any breeder suggestions, but I can offer some advice that applies to most or all people looking for a new puppy.
Because you're looking for a mixed breed, it's going to be very, very tricky to find a puppy who will be guaranteed to look and act like your old dog when it's grown. When you mix two or more breeds, the results are far less predictable than with a purebred. For example, your gorgeous boy seems to have physically taken after his Yorkshire Terrier side in looks, with his color, pointy ears, and shorter (possibly docked by his breeder?) tail. However, a lot of dogs of this mix will look more Maltese, or somewhere in between. If both parents have to look like he did, you're not looking at a F1 litter, where one parent is a Yorkie and the other is a Maltese, but a litter where both parents are Morkies, correct? When you have a multi-generational litter like that, you can get puppies everywhere on the spectrum. It's possible that none of the puppies will wind up looking like the parents, unless the breeder you find has bred many, many generations of this mix and selected for dogs that happen to look like your boy did.
It's good to remember too that a new puppy will be its own dog, even if you get the exact same breed mix with the exact same looks - heck, even two purebred dogs of the same breed can have vastly different temperaments. It's important you go in expecting to get to know this brand new dog, rather than assuming they'll be just like your old boy and being upset when they do things differently, or are more or less energetic, or don't like his favorite treats or games.
I'm not against breeding mixed breeds, but I do expect breeders to be doing it as ethically and responsibly as a reputable purebred breeder would. Make sure you ask the breeder what genetic illnesses they're testing for, and what the results are for their breeding dogs. Sometimes this means they need to send in a sample of their DNA to make sure the parents aren't carrying the same bad gene where, if a puppy gets a copy from each parent, they wind up developing a disease. For example, both Maltese and Yorkie breeds can have Progressive Retinal Atrophy if they get two copies of the bad gene that causes this disease, which causes a dog to slowly go blind. Some health testing is evaluating the physical structure of the parents - like the knees - another common problem with small breed dogs to make sure the parents have exceptionally good, healthy joints so they're less likely to produce puppies who have serious, painful knee problems that need expensive surgery to fix.
is a list of health problems sometimes seen in Maltese, and here
is some info about Yorkie health, just so you can check things out and understand why these tests are important.
It's also important that you trust the breeder, that you can (if possible during a pandemic) see at least mom with her pups, and see for yourself that she's a happy, confident, well-cared for dog who's treated like a member of the family. You also want someone who's asking you questions, making sure you'll be a good home for a puppy, rather than just willing to throw a puppy at anyone with a credit card like the puppy isn't a living, feeling animal. It's sadly very, very common for people to make up excuses for why you can't see mom, or to bring "mom" and pups to you, when it's really just a random dog not related to the puppies, because they're covering that the puppies were bred in a mill or other mass breeding facility, with no human care or attention, possibly minimal health care, and totally unused to living in a normal human household.
Be wary of anyone trying to rush you into buying a puppy, making excuses for why you can't see mom or where puppies are being raised (again, we are in a pandemic, so you might have to settle for 'seeing' the house online, but trust your gut if anything seems weird), or who has a big sob story for why they don't have mom and need to place these puppies now, now, now. Because more and more people are realizing how terrible puppy mills are, there's a whole profession now of 'puppy brokers', who take pups from mills, pretend that it's their puppy or that they're the breeders, and make themselves look more 'acceptable' than directly buying from a mill would be, even though that's where most of your money goes to.
Be careful too of classifieds and websites promising things that are too good to be true, especially if they want you to pay a bunch of money to have the puppy shipped, or want payment through some weird service you've never heard of. Demand for puppies has gone WAY up due to everyone being home more, and scammers are taking advantage of that by 'selling' puppies that never existed. Again, read up on scams, trust your gut, and don't feel bad about walking away from a puppy if something feels wrong.