I have a TravelPro CrewSeries Plus from 1997. Here are a few notes in case anyone else tries this.
Many thanks to Kelly80621 who put me on the right track.

• The original wheel, with intact rubber, was 76mm diameter. The damaged wheel without rubber was 68mm.
• I bought a pair of 76mm skate wheels for $23 (including shipping) from Flight Attendant Shop. They were very helpful when I had questions.
• My axles were coated with surface rust, but a little sandpaper and WD40 made them serviceable. They're 44mm long, 6mm diameter, and are held on by a snap ring that fits into a little groove.
• The original snap rings were not reusable - they were brittle with age, and got stretched out during removal. I found new ones on eBay for $3. The proper size is 6mm (same as the shaft). They have to be "external snap rings" not "internal". That refers to whether the little holes that pliers grab are within the diameter of the snap ring or outside of it.
• Snap ring pliers were a headache - they come in internal, external and a variety of tip diameters. My first attempt with cheap pliers didn't work because the smallest tips in their assortment were.047". Turns out I needed .039". I wound up with better quality pliers from Walmart for $28 (ChannelLock model 926).