Internal Credit/Cash System for Barter Site

[CasualConvo]

Hello. I don't know if this is the right forum to post this thread (if not, please remove) but I need to know if a mod already exists that's connected to either a classifieds or shopping cart where members can use real cash from say "PayPal" but also has it's own internal account balance system that can be used to purchase products too?

I've seen some mods that showed promise but their credit system seems to be connected to your activitiy on the site itself. I'm about to start a barter company and just need something where I can add and subtract dollar values from member accounts so that they can be used to purchase products on the site or use real cash if they so choose.

Thank you for your time!