Sometimes there's a mod that you just can't find on CurseForge, what do you do?
It's entirely up to the author of a mod to upload it to CurseForge, however, if the mod is hosted publicly, has a proper license that allows us to distribute the mod, and you can provide us that information we're happy to add it to our Approved Non-CurseForge Mods list.
We recommend first checking the list to make sure the mod you wish to add isn't already on there, and if not you can submit the information for review - Submit a request. It can take several days for a review to occur.