The closest campground (A) will likely be book solid, but you can call. The second closest campgrounds (B and C) are not too far and will likely have room. If you just want a place to park and sleep in your van you can use my driveway
A- Hershey Highmeadow Campground, 1200 Matlack Rd
Hummelstown, PA, (717) 534-8999
B- Hershey Conewago Campground, 1590 Hershey Rd
Elizabethtown, PA, (717) 367-1179
C- Thousand Trails-Resort Camping, 493 S Mount Pleasant Rd
Lebanon, PA, (717) 867-5504
D- Hershey Swap and Race