Found a piece of material for the canopy strut mounting blocks. Not sure this is the right material, but it'll work.

Then, I mixed a small amount of epoxy and flox to create a slight buildup at the location of this one rivet hole. See, this rivet hole is actually on the bend of the canopy skin and the canopy frame. But, since the bend radius of the canopy frame is larger than the skin, there's a very slight gap under the skin. Squeezing a rivet at this location will surely make a nasty dent in the skin unless I fill that gap up. Epoxy and flox to the rescue.