Well worry not! Some random website that I've never heard of is taking pre-orders for the 4 pack.
But these are pre-orders...so this might mean these are about to become readily available everywhere!
At least I hope this is the case. Anyway, you can find the website below, and the ponies for the easy price of $10.50.
FiM 4 Pack
Thanks to Muffiekun for the report!