It's going to be tough to get any of the smaller dwarfing rootstocks; most suppliers are sold out years ahead because of all the orchards switching to high intensity management systems. Even the Bud 9 you're able to get isn't very good grade. You can start looking in September to order for spring.

Raintree Nursery sells some EMLA 27 rootstock that's dwarfing; it may be the only ones available.

Applenut

Treco in Oregon carries P22