Just a follow-up to my first post. I went to eBay to look for a replacement touch panel. I found 4 that were close enough to try, and they were all cheaper than buying an entire new 7" PanelDue. My main considerations were the length of the flex cable and its placement. The cable placement on the best touch panel was off by about 2cm, but the cable was longer, and it reaches the connector on the LCD PCB without a problem. I will need to secure the small loop of extra cable, but that should be fine.
The other spec I didn't consider was whether the picture in the listing was of the front or back of the panel. Besides affecting which side has the adhesive (a minor inconvenience), turning it over also reverses the cable placement (a MAJOR inconvenience). I ASS-U-MEd they were all showing the front side of the touch panel, as it would be mounted on the LCD. Nope! Luckily, the one with the correct cable placement was correct.
Anyway, I just wanted to provide the eBay link to the one that works in case any of you have your own clumsy moment. Ideally the cable would be about 2cm closer to the center, but as I mentioned, this one works.
https://www.ebay.de/itm/7-4Wire-Resistive-Touch-Panel-Screen-7inch-HSD070IDW1-800x480-LCD/170844224701?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649