Help, please

[Jens Westerinen]

Hello!

Can't get the knobs off of the pots on one of my Smiths.
Will have to do something drastic to get them off.
The patterns in the stop screws (right? don't know the right English word) that holds them are busted so the hex key wont grip them.
What measures is it on these screws? mm or inches? Need to know when I buy new ones.
Anyone who can tell me where I can buy them where they ship internationally?
Or if someone kind enough could buy some and send to me.

Thanks!