Ask HN: Unique Thank You gift to engineer for work?

I got one of these circuit board pens. I think they are pretty cool. https://www.etsy.com/market/circuit_board_pen

Drones with video cameras are pretty cheap (~$50 for a small one) and fun, I guess?

You could try a bottle of some fancy drink, alcoholic or otherwise (and it could be easier to find something good in the latter category).

you should tell their boss.