What is a good word for a person selling to a merchant/shop? [closed]

I'm making a website which is a marketplace for in-game items with in-game currency.

Players can list items they are selling with a description and price. There's also a possibility to list items you are looking to buy the same way.

I thought a good word for the listing owner would be "Merchant" (is this right?). But what would a good word be for the person that buys or sells to the listing owner? Is client or customer a good word or can those only be used if you buy an item?

Sample:

Blackmarket advertises their item in a "listing". Gamerboy69 buys an item from blackmarket. Gamerboy69 is the customer/client. Blackmarket is the merchant.

Can i use the words in the same way if Gamerboy69 would sell an item to the owner of the listing, or is there another word i can use which will work?

Solution 1:

You could consider words like vendor, broker, dealer, or distributor instead of merchant.