That's a pretty cool idea. I have several spotlight projects that I started, but didn't finish due to indecision on how to get the heat out of them. This one has an aluminum body and would probably be the easiest to heat sink. It's the one that I plan on finishing first (MTG2 and stock reflector). I think the reflector is around 4". It's pricey though. I paid around $43 on Aliexpress.
Let me know if you want anything measured on it.