Welcome to YT.
You have come to a great place to better enable you to make a more informed dececion when selecting a dog.
I would suggest that that you research breeding ethics before actively trying to acquire a dog. Purposely breeding mutts is generally frowned upon for various reasons. You will not likely receive any responses encouraging you to support such shady breeders by buying a dog from them. I wouldn't consider a Morkie breeder going out of business as "unfortunate" at all--I would view it as a blessing!
Also, please be aware that even if you find a Yorkie/Maltese mix, it is not likly to act like or even remotely resemble your friend's dog physically. There is no set "type" for mixed breeds--you never know what you are going to get, including physical structure, temperament, or genetic ailments.
If you are determined to get a mix of some sort, then please consider adopting form a a rescue. Rescues need a loving home too and you would be granted them a miracle instead of supporting a bad breeder.