Roger - there is an old thread
at this link that Mark Wolf (Previous Loco Lobo owner) participated in. Based on
class rule changes in 2008, you have some flexibility on a replacement stove.
The J/30 full class rules are available from the top menu under "Class", "By-laws, Rules, Specifications".
On Rhapsody, I use an "omelet stove" that has the replacement Butane cartridges.
ps - welcome as a new J/30 owner!