I'll direct you to a link but want to offer a few words of advice first. A conscientious toy breeder doesn't breed down for small size. They will be breeding to the breed standard, so 8-10" is going to be most of what you'll find from them.
The smaller/smallest toys are often that way because dogs with genetically short legs are in their heritage. That's not to the breed standard. Smaller/smallest bred toys are more likely to have health issues, and be more subject to serious injury from a minor accident.
I'd strongly advise to pass on any breeder offering "tiny" or "teacup" toys. Those are strictly marketing gimmicks. In the US purebred registries, there are only toys, miniatures, and standards.
Ok, now for the links. This is a geographic breeder list which also contains a lot of additional resource links:
GEOGRAPHICAL BREEDERS LIST AND ADDITIONAL RESOURCES PLEASE READ THIS FIRST What this list is NOT: This list is not an endorsement of any breeder by Poodle Forum This list is not a list to just go buy from without doing more investigation This list is not comprehensive What this list IS: This...
I agree with others about caveat emptor when it comes to breeding to downsize and using those terms to market, but that said any litter will have potential variations in finished size and you could ask for a smaller pup, but I am not sure why most people would do so unless your housing situation leans in the direction of smallness. Personally I would be afraid of having really teeny dogs since I would worry about tripping over them and/or crushing them underfoot.