If you really wanted to solve this problem, one solution could be a metal reducer plate to 2-1/8 inches. (about #11 metal with a machined ID surface). Around the outside of the inside diameter you could drill holes mathematically calculated to emulate the amount of water that bypasses using the kitchen strainer thermostat. In that way, you could just use an everyday 235 thermostat and it would work (from what I understand anyway) about the same as the original. But a person would have to be highly motivated and I am not sure the amount of people who really care. Like Matt says, just order a THM 155 although, if 155 means its a 160 degree thermostat, that's a whole nother can of worms since the Kitchen Strainer is a 170 and my other example is a 195. This reducer plate I am speaking of would allow you to put whatever temp thermostat in you wanted.
Your solution would not work the same as your strainer type T-stat. I believe the strainer T-stat had a gasket around the top that seated against the radiator outlet. When the main outlet valve is closed (cold engine) there will be flow through the bypass only. When it opens there is flow through both.
In your reducer with holes solution there will be flow through both as you havent closed the radiator outlet. All you have done is bypassed the T-stat, not the radiator which would make engine warm up take longer.
Mike B
