copper slug

What for? to replace a fuse?
#2 or #3 should fit....check an AWG Wire chart.
For metric fuses? Again, check the chart.

Even scrap is getting expensive. Last year i replaced a faucted and got 11$ at a scrap yard for the one I took out.....Solid brass, Chrome plated.

If all you intend to do, is eliminate a fuse: solder a large gauge piece of wire across the fuse holder's terminals. Replacing a fuse, with a piece of copper, just provides two more contact points, for corrosion to form.

I must say I'm quite alarmed how non-chalantly this discussion has turned to materials for bypassing fuses . . . I'm thinking perhaps this may be a Bad Move from a safety standpoint.