Thanks, I ended up buying an "architect's lamp" from Home Depot that is just about perfect. It's a stand instead of a clip on, so it's hanging out pretty high over my tank, but easily adjustable, and since it uses screws to tighten, it can hold its weight nicely.
I'm pretty happy with the hardscape, I have a few places I want to add some more substrate, and I am still trying to figure out if that's the best place for my heater behind the tree. It's invisible, but blocks out some of the best background planting places, but it's so BIG on this tiny tank. I maybe should have gone for a smaller round heater instead of a large flat one, we'll see.
My next big question is what is a good plant to use for bettas to rest on, you know, big leaves that they can take a lazy Sunday nap on?