On a different forum someone was talking about a couple of chinese sites that have USA warehouses and sell great RC cars. So I went to the site and looked around. They sell, for a different purpose, a (roughly) 6" high light bulb for growing plants. Of course re-purposing that was the first thing on my mind...
http://www.gearbest.com/pots-planters/pp_308005.html?
It only costs $4.36 and is flat on the bottom so it can stand upright. Clever reuse of light bulb factories. Photos are swiped from the reviews.