I have the same folding 4x8 HF trailer that is sold now, but when I bought mine about 15 years ago, it came with the 8" wheels. I still use it for hauling building materials, moving stuff, etc. The 560x8 wheels and tires came off an old boat trailer that I junked. They are heavier than the original 460x8 wheels that came with the trailer and run with about 50 PSI, so the trailer handles well at speeds and heay loads. Still, for a camper, I'd want larger and will use 13" trailer tires and wheels like I put on my bass boat trailer that I have now (or larger if I find some at reasonable prices). These are standard white spoked, 5-bolt pattern and have ST175/80D13 tires rated for 50 PSI. I got them at a local Tractor Supply Company. If you have one in your area and haven't looked inside, do so. They have lots of trailer stuff. Check their site to see where the nearest one is located. Click on About TSC, then on Stores by State.
http://www.mytscstore.com/default.asp
For some reason, I can't find the 13" tire/wheel on their web site, but they do carry them in our stores and other sizes as well.