OK- so a quick update on what I've tried the past few days-
I got some soft white halogen 60 and 75 watt replacement bulbs from walmart- was 4 for about $6.
I also got a zilla mini halogen fixture and 50 watt bulb. $20 for fixture and $10 for the bulb.
I also got a 45 watt halogen spot from lowes. I think it was about $5
And I also found a clear halogen 100 watt replacement bulb at lowes. $2
The 60 watt replacement bulbs are OK- the 75 watt replacement would possibly work in my situation.
The zilla mini-halogen seems like a really good way to burn a lizard, and the light is so focused that it puts out hardly any usuable ambient light outside the spot and seems incapable of creating a gradient in a screen enclosure. It is hot hot in that spot though.
The 45 watt halogen spot was OK, but seemed a bit dim and not very warm. maybe a larger watt would work OK.
But my favorite by far was the clear halogen 100 watt replacement bulb. Looks a lot like a clear light bulb with a small halogen bulb inside the outer bulb. 72 watts. The light and heat penetrate all the way to the bottom of a 3' high screen cage, and creates a true thermal gradient when used with my 10.5" clamp dome reflector. The light is clean and white and bright. Might be a little on the strong side heat wise- didn't seem too hot, but at the moment I am having to refigure out the heat properties of my rebuilt building, along with far fewer enclosures. I saw a 75 watt replacement size of this bulb also at lowes- and I'll be checking that out to see if it is a better fit forlight my needs. But I'm pretty excited about these bulbs- I actually like the 72 watt 100 watt replacement bulb that I've tried better than the old regular incandescents. The light is so much brighter per watt- even brighter than the halogen soft whites by a lot too- and looks really nice and the heat gradient is better than a 75 or 60 watt incandescent too- the heat spreads further down from the bulb, yet it isn't super hot close to the bulb either.
That's probably the route I'm going to go with.