In case anyone is interested, I’ve designed up an Enders funnel in cad and have ordered a sample from shapeways to test out on my stoves. Due to cost, I’m having them made from glass filled nylon and I’ll be threading them myself. These are $16 a piece plus shipping. I can email anyone the step file if they want to do the same and Ill post results here from my test, but I’m pretty confident this is going to work. If anyone likes it and doesn’t want to mess with the process, I can make you one. A one off from me would cost about $35 (shapeways is $10 shipping, plus my shipping and my time to die cut and deburr), but several would reduce the cost. Stay tuned for the results. The thread is an M12x1 assuming that I measured it correctly.