M_Boats: U-Channel

For those with the older M17's with aluminum frame windows, have you ever replaced the windows, and if so, where did you find the rubber U-channel that holds the glass inside the frame? The stuff looks like this: http://catalinadirect.com/vinyl%20glazing%20channel.html CD only stocks a 3/16" glazing. The correct size seems to be 5/16" x 5/16", with a 1/8" slot or groove for the glass. Glass shops say they don't have it and don't have a source for it....ditto the auto glass shops. I'm trying to avoid simply bedding the glass into silicon or some other sealant, as it would be a bitch to clean up if you took it apart again. Howard