Where are the rules for the Gondola mentioned in A&EG?

My players are chomping at the bit to get an airship and since I’ve allowed the Arms and Equipment Guide in our campaign, they’ve naturally set their sights on the Soarwhale.

The problem is, to ride the soarwhale, you need a howdah or gondola. The rules for the howdah are earlier in the book, but I can’t find any further mention of any rules for the gondola. Are these printed in another book somewhere? If not, is there an equivalent somewhere? I don’t think the howdah is going to suit them as it’s fairly small.