I assume that the 3" TH uses the same towers as the 2.5" THs.
If that's correct, there are two kits available -- the Netkidz tower kit and AW's tower/heat sink kit. You supply the LED, the driver, and the labor to assemble into a functional LED tower.
Occasionally, built towers go for sale on the B/S/T forum and on CPF MP.
Thanks I have one of those on order for my M6. I was hoping to get one for the 3" T-Head as it has one of the tightest beams I have ever seem and it would be a real thrower.