Finding an alternative to a specific transformer

Are you looking for a commercial part for production, or a one off? It shouldn't be very difficult to make one like this with a small gapped pot or EE core. A turns ratio, primary to secondary, between about 1:5 and 1:8 should work. I base this on the 24 volt zener clamping the primary overshoot (that the effective primary voltage must stay below) and the 90 volt output.

How about e-mailing Linear and asking for more information about the transformer? Its probably obsolete, after the almost five years since the application note was written. It may have been something they had in the lab that would work, and is even older.