I use desk lamps with max 40watt bulbs on mine. A little warmth, but it doesn't really affect the temp, nor will it heat the lid too much. I use seran wrap taped over the top with holes in it to keep in the humidity to help the labyrinth organ and 40w and under has no effect on it, melting wise.
If you have a Penn-Plax New World Habitat as your Kritter Keeper, you can get the New World ThermaLight that fits onto the clear plastic flap. But from the looks of it, your kritter keeper is not a Penn-Plax. In that case, this might be your best bet. I've looked at it in the store and as near as I can tell, you stick this light on the tank wall INSIDE the tank. It won't be super bright but it does come in a variety of colors so you can get more than one.
I didn't know Lee's made led lights!! I just have a desk lamp propped up on bamboo stairs (they're actually floor samples) and I bed the light straight down over the water. The KK cover, being all holey as it is, diverts and blocks a lot of the light so it is not too bright. The bulb I have is 60W and while it warms the top of the KK it doesn't change the water too much if at all.
I have no idea, I just saw it online. You could probably just call your local petstores and ask if they have it. Maybe even try walmart, I know my walmart has kritter keepers with the rest of the fish aquariums.
I'm using a clip on lamp. ::) You know, the type you see sold for dorms? The lid diesn't fit on completely with the lamp there, so I bought some needle art canvases and cut it to the size of the top of the tank so the fish can't jump out. :)