I didnt realise how long ago it was but after watching the video it was over ten years ago, I made a graver sharpener https://www.youtube.com/watch?v=8okY...channel=Josef1 sorry for the annoying sound!!
today I I found this on amazon
and with the fine one of these

I recon you could make a pretty cheap sharpner even better if you could secure the lap with magnetic tape. I know its not GRS but it is lots more economical !

I've not tried it as I still use the one I made, I am tempted but it may help someone out if you like a project in the meantime.