There's also a satoshibox clone script for sale here, that you could host on your own servers: https://bitcointalk.org/index.php?topic=2258851.0
I just checked and it seems the sale is still ongoing for that script.

Otherwise I can't think of any mainstream alternatives, other than those already mentioned in this thread (e.g. Satoshibox, Rocketr).

For physical goods there is https://www.peerhub.com (payments with Steem) but if you were using selly.gg I imagine you're looking for a digital goods store, not physical.