Derek -
If you want to use a Pa. nursery, Musser Forests has Washington hawthorn seedlings of 8" to 15" for $1.78 / each if you buy 25, and $1.02 / each if you buy 50. I have some spruce and chestnut oak seedlings coming from them in the spring. Less shipping cost using in-state nursery.
Cold Stream Farm in Michigan also has them. I have seedlings coming from Cold Stream too in the spring. I've never gotten bad stock from Cold Stream - always nice stuff. I've gotten various seedlings from Cold Stream over several years. A little more to ship from Michigan, but the stock is good, so I pay the extra shipping costs. Either nursery should get you nice stock. Washington hawthorn grows pretty fast, especially if you toss down some 10-10-10 around them each spring. 15" seedlings at camp grew to 6 ft. tall in about 4 or 5 years doing the 10-10-10- thing in April each year. Deer WILL nip the young twigs that don't have thorns on them yet, so I cage ours until they get to about 7 or 8 ft. tall. By then they have enough UGLY needles to survive any deer nibbling. Once the needles appear, the haws self-protect, really.
EDIT:
I just checked Cold Stream for Washington hawthorn seedlings. They have 1' to 2' seedlings for $2.45 each if you buy between 25 and 99 seedlings. If nothing else - read the write-up on Washington hawthorns on the Cold Stream site. They're listed under "deciduous shrubs" because they don't grow really tall like regular trees. ( Our oldest haws are about 16 to 18 ft. tall after around 20 years, but they got partially shaded by pines until this September. Now that they're in full sun, they'll grow taller and fill out even more & produce more red berries). The positive attributes of the haws are pretty well listed there, including what critters eat the red berries.