Looking for na Theme with a merchant login?

Hi, im building a website for my client. They are a distributor for wholefoodss. And we want to create a website similar to a webshop, but the webshop is only avaialble to view for granted merchants accounts. Basically we will provide merchants with a exklusiv password to see the content/products on the website and from there, merchant can place orders. Merchants will all get their own Username, password login.

Can anyone recommend a good theme for wordpress…?