Not gp, but here are some: https://diyusthad.com/2021/04/top-5-open-source-smartwatch.h...

Check out Watchy. $40. If you search for ESP32 based watches, you'll find plenty. Not all that good looking, but you can probably get one for under 5 bucks.

There's so many these days. Just have a look at AliExpress. There were various KS/IGG campaigns, too. One thing which kind of stood out was a smartwatch remote with what I will summarize as 'Flipper Zero capabilities'. I think I saw it on Etsy. It looked terrible though. For red teaming, you'd want something which looks professional, and blends in. Ideally with a watchface as, ehh.. 'screensaver'.