Yeah, unless you can find one on Ebay, you're going to have to spend about $20 on a good wheel. Definitely get a 12" for your boys, the one in my Coast Cage is 11" and it's almost too small for Jellybean.
Expect to spend about $20 ($25-$30 w/shipping). The wheel will last you a long time, and you will have to listen to it all the time (if your rats actually use it). My cage came with a Super Pet Comfort Wheel, it's probably the second best wheel on the market (I would expect Wodent Wheels are better, but I've never had the joy of owning one yet). Don't get a wire one, or one they can catch their tails in. The comfort wheel I have is decent. A little noisy, but I can sleep with it. I oil it with cooking spray to keep it running smoothly.
Also, you can try to find one on Craig's List, though I don't know what luck you'll have.