Glue?
Glue?
Stinger,
A few quick thoughts. If the area's not stressed, and you wouldn't be if it looks a bit odd, you may be able to get away with using clear caulk. Or a combo of the clear caulk and a little piece of whatever clear plastic you can lay your hands on that'll work. In the gallery there was a guy who "extended" his blower outlet to filter transition with some pieces of very thin and flexible polycarb and a fair amount of clear caulk. Could probably hunt it up in relatively short order if you wish. If admittedly faulty memory serves, think he got it from a crafts shop, like AC Moore or Michael's.
If it needs to be stronger, I forget if its acetone or methyl chloride that's the glue for PTEG. If you go hunting around Lee's Shark Guard, Lee lists some vendors for solvent glues for polycarb, and going to one or more of those will yield the right solvent glue for PTEG.
And finally, if you rough up a small surrounding area with a bit of sandpaper, you can use fiberglass and epoxy, as both I and Steve (Woodman) did to assemble our inlet transitions. Doesn't end up as clear as glass (or the original) unless you spend a whole lot of time polishing, but is translucent enough to be reasonably unobtrusive. The epoxy only needs surface roughness for "bite", for mechanical adhesion.
Regards,
DWD