I have mercs of all decades from the 50s to the 00s, and even a 175W Philips from 2010 I bought recently! I have only one from the 50s though, my Westinghouse H33-1-GL/C Lifeguard WeatherDuty.
It's hard for me to find vintage lamps (except for incandescents, but those are my grandpa's, not mine). I'd love a vintage merc or two if you come across them!
Try eBay and Restore, that's where most of my vintage mercs came from. Some hardware stores might still have vintage mercs but you'll have to get really lucky to find one there.
I swear, the /Ws are almost chasing me!
Michael: It's not that hard to find vintage mercury lamps. I can find some for you if you want!