I agree, this is the perfect idea </sarcasm>, but how did they get there? I propose three solutions
1st: We've already seen the girls are capable of tool use (in that one inaccessible cave) so what we need is them having a small but nifty looking wood lathe, probably hand-cranked that's specifically designed for strap-on production, that would explain everything in game...except how the fuck did they get hand-cranked lathe for strap-on production.
2nd: Oh no, the evergreen ship has managed to wedge itself between two landmasses again, and the furry girls have looted it for all the strap-ons from that one Temu container or something.
3rd: there might be a way for a dick-shaped shrubbery with convenient straps made out of vines to be possible.
I still however fail to see, why a realistic looking dick on a furry is more weird than fake looking dick on a furry.