My kids use an educational app series called Osmo, which comes with a reflector like this for iPad (1). Field of view and distortion may be an issue, but I bet a vendor could easily make something similar designed for this use case.

It also looks like there are $6 clip-on mirrors (2) that would also do an admirable job, perhaps with more stability and control than the pencil-balancing trick.

(1) Osmo - Base for iPad https://smile.amazon.com/dp/B07JNZ4J67/

(2) Flexible 4" Clip On Mirror for Computer Monitor - Convex Desk Mirror to See People Behind You - Perfect in Any Office Cubicle Environment https://smile.amazon.com/dp/B078NB3JV2/