It's those regular whatcha ma call it lights. The ones that you can insert a single bulb into and it has the clip on arms. Something similar to this (couldn't find a better picture).
You can get them for under $10. I bought a $15watt tank light from Petland and that works fine.
Home Depot Has Ones, See If You Know Anyone That Had Reptiles And Has Light A Heat Lamp.thats What I Have With A Reg Pc Bulb Over Mine And It Works Great. I Think It Has A 21 Watt Bulb. Its Perfec, It Doesn't Dry Out The Leaves On My Mangroves