Hi Alan (and sorry Adam!),
honestly I wouldn’t use beeswax. Accordion manufacturers use it to fix single reed plates to the reed block to be able to remove them without a trace, but it hardens and you will need something flexible to prevent leakage. Instead you could buy straps that accordeon repairers use to tighten the bellows which are available in many sizes and diameters.
This is a german site but you can fand those straps everyplace.