Retailer Web Portal Website

We need a retailer web portal that would be made in WooCommerce or Shopify. The website would only be accessible through a log in (which would allow someone to sign up but they have to be approved to see the site). You would have to import about 500 items from our current Shopify site to the new website. The customer would be able to add items but when they go to checkout it will not charge them and notify them that we will pull their order and then invoice them based on what's available. Example website of something similar to what we want is ----------