I make my own heat panels from heat cords of various wattages depending on the size of enclosure I want to heat.
I weave the cord of whatever wattage I need onto 25mm x 25mm welded mesh, frame it with narrow timber battens, cover with black or green shadecloth (50% or less, this is very heat resistant, and doesn't come into actual contact with the heatcord anyway) and attached either on the ceiling or the wall of the enclosure.
The open structure of these panels provides very good circulation (no hot spots develop) and the shadecloth never gets very hot, so it doesn't matter if the snake lies in directt contact with it for a period of time.
I have been doing this for 6 years now, have never had one fail, never had a burn, or any problems whatsoever. Because the cords are waterproof the panels can be misted without fear of shorting them out, and the shadecloth holds a bit of moisture for a few minutes until it evaporates, ensure a quick rise in humidity. I do this especially when I see or expect a snake to shed.
So... you can make your own very effective heat panels for less than half the cost of those commercially available in Oz...
Anybody who is interested - I have some photos of the process, pm me with your email addresses and I'll shoot some to you (not sure about posting photos here!)