Based on a tip from a thread in this forum, I found this faux leather 5" gps cover. Amazon $7.99. The mini fits very snug in there and the stiff arms of the cover protect the screen without adding too much bulk:
AmazonBasics Faux Leather Carrying Case for 5-Inch GPS
I never would have thought to shop gps covers without reading it on these forums, but it worked out for me.
I wanted something that was really inexpensive since it didn't make sense to spend $25 or more to protect a $70 mini and, even more important, I didn't want a cover that would add a lot of weight and size and negate the portability of the unit - which is the feature that led me to buy it in the first place.