Domainers buy domain names to fellow domainers too! There are times where they contact an owner of a domain name and send an offer for it. There are also times that domainers who wish to buy a certain category of domain post a request and let fellow domainers send in their available domain names for sale.
Aside from that, domain buyers also include requests such as that if a fellow domainer can provide a domain name that fits their requirement and is available for registration, the buyer will send in a finder’s fee. The problem with this finder’s fee is the integrity of the buyer whether he will pay for it or not.
We cannot exclude the fact that the buyer may register the suggested domain name without paying the finder’s fee he so announced. We can’t obliged the buyer to pay it, if I am right on this matter. For one, the buyer is not infringing any copyright there. And two, the domain name is available which others are just not aware of.
But thinking on the bright side, you may be able to send out your suggestions to a buyer without expecting any return at all. After all, why don’t you just register it on your own and sell it to others or develop the website? You can think of it as a help to a fellow domainer which may need that kind of domain for his/her project. And if you don’t trust the buyer at all, then just leave it.