There are currently six butterfly farms in Belize, and Shipstern's is not by a long shot the best of the six. In fact, it is barely a butterfly farm anymore -- there are just a few butterflies kept for educational purposes. They no longer export pupae.
The best is Green Hills at Mile 8 of the Pine Ridge Road in Cayo. It is run by the fellow who used to run Shipstern, and his partner.
There are also small butterfly centres at Chaa Creek and The Trek Stop (both in Cayo). There is a sizeable operation at Fallen Stones near PG, and a community educational display near Lamanai.