Bike Rack Mount Mount (West Seattle)

Local Mail Carrier here, I am starting a part time delivery job soon and would like to use my bike to make deliveries but am in need of rear rack mount for my bicycle. I all ready have panniers but have no way of attaching them without a rack that goes behind the seat. Or if you know anyone that may have one available I’d really appreciate it if you point them my direction. I’m willing to work for trade whether it’s yard work or handyman type things I’m fairly crafty and a good honest worker. I know this is a “free” site but I thought I would put that out there. you have one you could spare I would really appreciate it. Thanks