Namely things like "Large leaves" and "Rocks" or "Large Rocks," especially when we have 15+ copies of the same materials.

I was hoping to be able to sell these at MonkeyBusiness, but the option is not available and I'm doubting most people would buy them because of their commonality.

I think, if you can't sell them, perhaps give people the option in explore to take them or not. Something like:

"You found the perfect [insert item] for hiding your den,"
[Take it] to use, or [leave it] for someone else to get?