I took a picture of the top of my tank so that you can see why I cannot simply add a reflector with a heat lamp on top. As you can see the top is made up of two pieces of glass, separated in the middle by a 2.5" strip of wire mesh guard.

I agree with you Amy that adding the bulb guard on the inside will allow the bulb guard so hang too low (since the tank height is not much). But what other options do I have? And yes I did a search for other bigger tanks without any luck.