Reddit mentions of Tombow MONO Zero Pen-Style Eraser Refill Round Tip + Square Tip + 4 Refills (Silver Barrel)

Nice collection! I have a few more items for you to consider adding, should you be so inclined:

• Uni Kuru Toga Pipe Slide: Plastic variant of the same line but with a retractable tip. Although I prefer the feel of the Roulette (which you already have in silver), I carry the Pipe Slide in my shirt pocket every day because it won't poke holes like the Roulette does. For those unfamiliar with the Kuru Toga line of mechanical pencils, they automatically rotate the lead every time you press it to the paper, avoiding flat spots and keeping it sharp on all sides. Note that this occurs each time you press down, not as you keep pressing. Thus, drawing a line rotates one notch (because you only set the tip to paper once), whereas writing letters, dots, etc. rotates multiple notches as you continue to repeatedly press the tip to the paper for each character.
  
• General's mechanical eraser: finer tip than most mechanical erasers, and nice pen-style grip. Refills are also available but I've found they're often cheaper locally. (Amazon sells 3-pack refills for ~$4 but my local college art store sells them for half that.)
  
• Tombow Mono mechanical erasers: Extremely fine erasers for detail, more than even General's, for uses such as erasing small lines while drawing. You can order sets of both shapes (round and rectangular) or just one, and they're available in silver or black.

I used one of these for 3 years of my undergraduate physics degree, and then for all the classes in my phd time. Still have it, love it. If I need to write something in graphite, this is my go to tool.

Also, if you need to do precision erasing, pair it with one of these:(https://www.amazon.com/Tombow-Pen-Style-Eraser-Refill-Refills/dp/B00ZZ4PJRA/ref=sr_1_7?keywords=mechanical+eraser&qid=1571968831&sr=8-7).

The mechanical eraser isn't as high of quality as the mechanical pencil, but for precise erasing like I sometimes needed to do in equations, its the best I've ever seen. Obviously use a regular eraser for bulk erasing (or just toss the paper lol).