Last time I went into my local Radio Shack, I found they didn't stock 50 ohm
coax anymore.

Sad but true. From what I understand RS made nothing from their electronic
parts, did it as a favor to us experimenters. Must be same with coax now. How
much could they make on a 10 cent resistor pack?
I hope they keep the parts section open, but afraid it won't be much longer.
73 Gary N4AST