Finding sires and dams for your model horse has become a lot harder to do from when I first began collecting model horses. Finding fantasy breeds is particularly challenging. A lot of websites are down, others are abandoned, and the list databases were so flooded with spammers that they are out of date from not being kept up. So I have spent a lot of time going in circles trying to find people who still do pedigree assignments for their model horses. This is a list of people I have found.
Elk Star Ranch (nonaging allowed, fantasy breeds)
Thundervalley Farm (fantasy breeds)