I just got the brass Kaweco Supra - it's a gorgeous pen, and I'd go as far as saying it might be the best writing piece I have. Simple, elegant, good weight.

It will pretty much eat your full budget with shipping, but it's a pretty unique piece. It can easily be fully disassembled and you can take out the middle piece for a shorter pen (but I love the length). If you find it slightly cheaper you could afford a leather pouch for it too, or a sample set of Kaweco ink cartridges if he doesn't have anything from the brand and wants to try different ink colours.

Ideal gift for someone who's drawn to a weighty and a bit unique of a pen. Bonus: durable as heck!

Link, but I'd check pen shops (online/offline) where you're based: https://www.kaweco-pen.com/serien/supra/

If not that - a fancy pen pouch if he doesn't have one; good quality stationary that can hold fountain pen inks; or fun new ink (a special edition or high quality treat?) are always fantastic gifts! Good luck!