Hi, I am looking for a site like this: http://www.thegreatapps.com/
Do you know of any on Envato?
Thanks
You could probably do it with one of the digital marketplace themes (may need a little customisation) like these.
Bear in mind that because people are charged to upload/use the site you will need an extended license to use a theme from here. These tend to reach into the thousands of $ so you may want to consider hiring a freelancer to custom build it.