@G3750 posted:
Girder and panel sets are still out there - saw a few on eBay that weren't ridiculously priced. A company called Bridge Street made them relatively recently (until 2016 according to Wikipedia). The one from my childhood is lost to the sands of time - as I remember, the panels and base weren't very durable. I have one of the Bridge Street sets that I've been meaning to assemble and place on the layout, but you know how that goes...