There are ways of building a hotend without kapton tape, if you are happy to have non insulated wires dangling about. There are other high temperature insulation materials, but kapton tape is easy to use since its just like sellotape that works at very high temperatures. However: DO NOT USE NORMAL ELECTRICAL TAPE ON THE HOTEND OR ON ANY WIRES NEAR THE HOTEND
It will melt and release lots of horrible chlorine based gasses!
The only place I have found to buy kapton tape is ebay, there is plenty on there!
I just used RTV red silicone, capable of about 360 degrees C. But before I stuck the resistor and thermistor in the head I dabbed them in a little thermal paste for better heat conduction. Then used the silicone on the outside to glue the parts into the head. It also holds the PTFE wire insulation in place.
I have only been printing on cleaned glass so I didn't want to buy kapton tape, this is why I did it that way.
Thank you very much, I've just come to understand that kapton is just to hold the thermistor and resistor in place, I was wondering what else could do the job and couldn't think of anything that wasn't simple and effective. But I searched for that silicon in the local hardware website and it seems they have it so ]I'll see if I buy it tomorrow.
@TerryKidd - Just curious, Do you use PLA or ABS? I've heard it is possible to print with PLA on bare glass, if the glass is on a heated bed and absolutely clean of oils and dust. I personally have not yet had an opportunity to try it, though.