(Bending plexiglass or lexan isn't as easy as it might seem.)
Here is the simplest way to add dust collection to an IBOX.
I'm not positive, but believe I may have used the flange and a right angle fitting that mounts to the end of an INCRA router table Wonder fence. You can see I enlarged the opening in the MDF guard and just attached the fitting flange with small wood screws. I quickly discovered I needed to angle the fitting to the right (or left) because if I ran the flex hose straight back towards me, the coils would catch on the table edge when I pushed the jig forward.
Wonder fence flange and right angle fitting? Other flanges and right angle fittings should work just as well. You could even enlarge the hole in the guard to match the O.D. of the right angle fitting for a friction fit..
Photos and Sketches of miscellaneous plexiglass/lexan guards:
I used a prototype IBOX so you may notice some differences in what you have- different stock ledge, mechanism lock, silver adjust knob, micro knob, etc. and a few extra holes.