He, he, heat is heat. I like the look of that!

Also seen once a dude using halogen spots as an IR reflow station for BGA (the 12V light bulbs with an included reflector, usually for embedding in ceilings and gypsum walls).
Everything packing a few tens of W in a small volume should work.
A good source for such compact heaters could be, for example, the incandescent light bulbs for cars. Some models of H7 headlights bulbs have a diameter of about 1cm and 2cm long, with 55W/12V.

A lot of power for such a small volume. The 24V ones can have 70-100W, can make a beefy soldering iron with such a lightbulb as a heating element.

Fit one of them inside each end of a copper pipe and you got yourself a 100W handheld heater for whatever needs. For example such a heated pipe would be good to bend plastic sheets to make enclosures for circuits, or for heavy soldering, as a solder-pool heater, etc. Or coil the copper pipe under an aluminum plate to get a heated bed for a 3D printer, IDK, things like that.