I just got a vacuum beard trimmer from Amazon. From reading many reviews in the category, this seemed like the best for my purposes. It's the Shpavver Vacuum Beard Trimmer. (Obviously, coming up with an English brand name is not their strong suit.)
I was able to go from a scraggly week of hair growth on my head to an almost invisible stubble. It's not BBS, but a quick wet shave would solve that. Using a razor on what I started with would have been impossible.
This version gets better reviews than the highly-promoted brands. The thing is even water-resistant at IPX6. Obviously, you can't dunk the whole thing in water, but you can rinse it out with water.
Just a first impression, but very favorable.