Adam..try
small parts for a bellows coupling. They are not cheap but they do have some cheaper versions. Sometimes they come in different in/out shaft sizes (
like this one)..some times they are both the same. That said they all appear metric and the Losmandy will definitely be imperial and the McLennan is metric.
If you buy one that has a some in/out bore....then bore the other side for the larger shaft.
Can be done in a drill press...maybe make a holder for bellows so it is kept perpendicular.
Sorry i don't know the Losmandy dimensions. FWIW.