Although I have an IR lamp, I’ve never used it for PE since I also have a Thermotex pad. This is much more subtle than a lamp, but find it needs a constrictor device of some kind to stop the blood from removing all the heat.
I think almost any physical block betwen the light and the skin will stop IR, or at least it will absorb the IR and heat up, so making sure it’s not in physical contact with the skin would probably work. I’ve read of people suggesting a sock or similar, but personally I don’t think this would be enough. Perhaps Aluminium/Aluminum foil plus an air gap might work?