Search:

Any indian store should have henna paste. just ask

Test it on a disposable blade first to see effects, might take a lot to buff off it it gets too deep in the steel. Apply with a tooth pick. Mash up the tip with your teeth to soften the fibres.

I was out buying some Hookah tobacco ( yeah I'm a big fan ) and I saw some henna paste there, the kind they use for temporary hindi tatoos. It was like £1 so I got a tube. Afte playing around with it...