OK, I just went out to my garage and dug through my drawers of old TT RV parts. I found several plastic drain plugs for my old Dutchmen TT water heater, anode rods for my Keystone TT water heater, door catchers, screws with the box head square head end, wire, window parts, an extra cap for my bumper, all sorts of stuff that I've collected over the years. Things I'll probably never use.
I did find the original gutter extensions that were on my Springdale still packaged in their replacement extensions (which were longer than the ones that came with the trailer). They were Camco and I remember we purchased them at Camping World.
I did a quick internet search and saw that even Lowe's hardware, building supply sells them now too.