The A-Zoom dummy rounds are a good option.
To do an inert round, you'd have to get a die to resize a fired case, and as rimfire are not designed to be reloaded, that could be tricky.
You could try and pull the bullet from an unfired cartridge, and try to insert it into a fired case, but not sure how that would go.
DO NOT pull the bullet from a live round, empty the powder, and refit the bullet. Even if you could do that, the priming compound would still be in the rim, and at risk of detonation. It would also still be classed as live ammunition, so would still need to be on your FAC, and stored accordingly. (which as you are asking for an inert round, I'm guessing you don't have WMR ammo allowance on yours)
You can start to see the challenges you are going to have. If you could detail how it is going to be used in your project, then SD may be able to come up with other ways of helping.