Wait that is a pen: Pilot G2 Retractable Premium Gel Ink Roller Ball Pens Extra Fine (.5) Dozen Box Black; Retractable, Refillable & Premium Comfort Grip; Smooth Lines to the End of Page, America’s #1 Selling Pen Brand https://www.amazon.com/dp/B00006JNJ8/ref=cm_sw_r_cp_api_i_MgrdCb7C7787W
The link I posted yesterday is an Amazon link to a 12-pack of the 0.5mm point...
https://www.amazon.com/Pilot-Retractable-Roller-12-Pieces-31002/dp/B00006JNJ8
A little calculator keychain or something would be cute
A rubics cube or some sort of fidget toy
Sudoku puzzle book
Chocolate [even better if it's like truffles or bites so that you can reward yourself after each chapter completed etc]
Waterbottle [could have a funny actuarial saying on it, I'm sure there's something on RedBubble]
If he studies on paper, then a nice notebook/notepad or pens [these are my favourite: https://www.amazon.ca/Pilot-Retractable-Premium-Roller-12-31002/dp/B00006JNJ8?th=1]
[I am an actuary but broadened it to be a little more mathy, plus things I would have enjoyed while studying]
It’s hard to beat the Pilot G2. The refills also fit in a lot of other pens.
https://www.amazon.com/Pilot-Retractable-Premium-Roller-31002/dp/B00006JNJ8
Here's an Amazon link for you.
pilot g2. nothing special.