A tool case that holds extra

Buy an electric hand tool like a grinder. Get a nice, plastic, case.

But the case does not have room for discs.

It is more a rule than extra ordinary that there isn’t room for drills in a case for a drill, discs for a grinders or sand paper for a sander.

The idea is that when a hand tool manufacturer sends along a case with the tool; the case should also be able to hold necessary parts.
It can’t be that hard. I create wooden boxes for my electric hand tools to keep all the extra stuff.