Does anyone know where I could find a place to sell unopened male in/out catheters? They are pre lubed, unopened and still in box.

I don't believe you'll be able to sell them but after my husband died, I donated his catheters(unopened)to hospice, and they were grateful to receive them.
Or you might want to try donating them to an Adult Day Care Center as I in the past donated my husbands diapers that were new and unopened. They too were thrilled to receive them.

In my area medical supplies are rarely returnable. Most people donate to nursing homes or other care facilities.

I would say that since you received no response, that no one has any idea. Will the place you bought them not let u return them?Bumping up just in case this post was missed.