There is a public demo here of OpenBazaar running completely inside Tor. http://g2h4k7gmeszbnouc.onion
They use Onioncat and there is also a Tor only seed node here : [fd87:d87e:eb43:ea68:8af9:e26c:eb65:e33f:12345]. I have successful connected an OpenBazaar node to that seed but it was a bit of an ass to configure as I had to install Oniocat and configure it.
This demo is documented here: http://thehub7dnl5nmcz5.onion/index.php?topic=5100.0