I know what you mean trying to keep things like they were original. I have drug my POPUP way back off the roads alot and have never had any limb damage to my RAIN GUTTERs. Sounds like another post here has had a similar thing like you with his rain gutter.
Maybe my lower height with the POPUP when being towed is the big answer. My truck pushes the limbs out of the way first before they hit my trailer...
I guess just contact the manf and see where they get their rain gutters from. I'm pretty sure mine must be spot welded on. Don't remember seeing any associated mounting hardware with mine.
Good luck on your search...
Roy Ken