This is borderline on-topic here as it's not really a vintage radio club. But the 'audiophool' thread revealed a number of people here like HP calculators, so I will mention there is still an active HP calculator user club in the UK (we accept members for all over the world, of course).
The website is
http://www.hpcc.org/
But that does not really give a true picture of the club. The reason to join, in my opinion, is the monthly meetings, held at Imperial College in London. At those meetings just about anything (technical) gets discussed. Old HP calculators. New HP calculators. Other calculators. Other computers, large and small. Vintage radio. Tape recorders. General electronics, old and new. Test equipment, old, new, common and obscure. Telephones (old landline stuff, smartphones, etc) Model engineering/metalwork. Steam engines. Car engines. And much, much, more
Anyone here would be welcome at a meeting as a guest, but please contact the club before just turning up. Or PM me for more details and information.