You may get enough flow by setting a small fan near the cage not inside, and possibly cycle it on and off with a simple lamp timer. It doesn't need to be a noticeable breeze, just some movement. Actually, basking lamps, foggers, and auto misters push the air around too.
If you use a cheap 40 mm pc fan it will work but can be a little noisy. Splice a 12v output plug like a phone charger and be sure they're rated the same. You can also get a fan controller, I've always wanted to try these. They can power 4 fans individually and has a cool LED look!