2 1/2" ports are hard to find. I custom made mine by cutting 2 1/2" holes with a holesaw through several sheets of plywood, stacking them together and glueing it behind the baffle.Alternatively, you can expand the port to 3" diametre and lengthen accordingly. 3" plastic ports are very common and I can recommend a place in K-W for you.
BTW, is there a reason why the terminal cups are on the front baffle?
Gar.