Thanks everyone for the feedback!
With a little bit of online searching (and learning about working with PEX), I determined that all the fittings in my Hi-Lo are manufactured by Flair-it
. They provide a PDF catalog (follow this link
or find it at the top of the home page) with parts and explanatory information.
I was able to avoid buying a new angle stop valve for $11 and simply replace the cracked valve top nut for $1 (I bought extras to justify the $8.30 shipping fee). That way I don't have to mess with the penetration through the floor for the cold water drain or disassemble the plumbing any more than necessary. The only minor difficulty was seating the valve stem back in the valve body in a cramped space using a mirror.
I know I could have hunted around and possibly found a suitable replacement locally, but I opted to go the OEM route with the manufacturer this time. I'll be back in business when the parts arrive, in plenty of time to continue prepping for a brief trip in a couple of weeks. Thanks again!