True 2.5" blast gates? I suspect DIY is only option.

[LCHIEN]

you could build blast gates like the DIY one in the video posted (yeah but be careful of that PVC pipe cut on the tablesaw...), except make one side with 2.5" and the other side with 4" and a 4" opening in the sliding gate.
You cold use a short hose between the gate and the tool to minimize the 2.5" restriction.