tartmode, [this](https://www.ebay.co.uk/itm/CNC-Machined-Anodized-Arm-Fixing-Bolt-for-Shimano-Hollowtech-Crank-Chainset/330831859440) works and uses a big Allen key which you already
Just the logo or #tartmode with initials/frame number two-pass engraving available.
![](https://lfgss.microcosm.app/api/v1/files/dec4b6f2abfd92174a7cd7eb1521bb059bef275f.jpg)