Need Plugin For

I am looking for a plugin that allows me to have a login for managers of car dealerships to buy my product, separate from the shop already on my website. The plugin needs to be able to ask them their name, company, PO, and what they would like to order. I think just a form that they submit would be good. But a place to manage their account would also be fantastic. I have no idea where to start looking. Help would be great!!