I have a standard policy that if a gallery or our local historical society recommends me for a commissioned painting, I give them a % commission (a finders fee). For the historical society, I want to support them, for the commercial gallery, any small business owner can always use a few extra $$. Just because I offer the commission does not mean they need to take it.
Maybe I am looking at your question from the other side--If I was a collector and the person who found the item for me, makes a living from this, or it's an oldgas member who might not have a lot of income, I would offer a finders fee. It does not mean they need to take it, but I wouldn't think less of them if they did. Hopefully they won't think less of me for offering. IMHO
