Some progress. I've found a company in Australia that will make multifocal lenses for dive masks. I also had an eye test today to make sure that my prescription was current. I mentioned contact lenses and the optometrist did some more tests and a fitting. I've been given a trial pack of contacts and been wearing them today. So far, so good. Pretty comfortable. Things have moved on in the 25 years since I last put the bloody things in my eyes. Close vision is not as good as with my glasses, but the optometrist said that was to be expected. Good enough though. I've never liked the idea of wearing contact lenses when diving, but could be a solution for now.