Pete - as Nathan said earlier, there are Scale train shows. I don't know where you live, but the next O-Scale West show (which explicitly includes S-scale - for some reason it isn't reflected in the title) is in Sacramento (CA) in May 2021, here: https://oscalewest.com/
Alas, one of their shows was where I let the SHS 2-8-0 get away from me (meaning I didn't wanna pop for the $500 for it). There is an S-scale club in either northern CA or the SF Bay Area that usually shows up with a layout and lots of folks selling lots of stuff.
Note added: The aforementioned O-Scale West show is in its usual haunt - the Hyatt at the Santa Clara (CA) convention center - not in Sacramento, which is what I said earlier (Sacramento is where O-Scale West is headquartered, not where their show is).