The soldering iron I have is this: ebay 58w iron, very cheap but effective.
It uses solid tips of 6mm diameter and I made a welding shoe from heavy copper tube, hammered flat and smoothed off to 11mm width. Having seen the clover iron I have bought a large shoe and will soon add a set screw to the iron heater to hold the clover shoe in place.
The original 70den/170gsm tpu fabric I got from extremtextil 5 years ago welds nicely at approx 280deg C, but the new lot just melts at anything more than approx 160C (the dial is not marked finely).