I'm supposed to vend 9 times for my quest, where should I go to do this/what is it?

There's one in Riverside, next to the hamburger. Here's a direct link: https://subeta.net/vending.php/dragonshoard#/home

There are other ones too that you can find listed at the top of that page. They're vending machines that give out random items, some of them have specific themes for a lot of the items. It costs Wizard Tokens to get items from them.