Ok, if you want to bodge this for less than a tenner then this is for you. If you're going to downvote me for doing stuff to *my* bike, jog on. First buy cheap brake lever guards from ebay... https://www.ebay.co.uk/itm/114304835495. They seem to have gone up, I paid £8.50. Remove the throttle bar end and bolt, leave the insert in. Drive a screw between the bar and the insert like this... I did say that this was a bodge but this screw will stop the insert from rotating and from vibrating. It doesn't interfere with the throttle tube at all. The bolt supplied with the cheap guards matches the original so use two smallish nuts to make a spacer, use threadlock and install the lever guard... ...and you're done. If you bought the kit I did from ebay you have a spare end piece and three spare blade bits. To put everything back as it was take the lever off, take the screw out and put the bar end back on.