You may also consider an M8x30mm DIN 6336 or non-DIN/ISO variants of hand bolts which are far more ubiquitous if matching the OEM look is not a concern. These come in 5-7 lobes and are available from the likes of ebay, amazon, etc.
* [https://www.mcmaster.com/products/knobs/material~nylon/stud-length~30-mm/thread-size~m8-2/ McMaster Carr]