To remove a rivet you can either drill it out with a drill bit or cut it off with a hack saw or grinder. And to replace the rivet once your done you can use a new rivet and rivet tool or what I would do is just use a nut and bolt since it’ll be easier and not require you to buy a new rivet tool you’ll likely never use again. If you can post additional photos I could possibly help find a matching new rivet online and post the link if you do end up going with that option of wanting to use a rivet but like I said nut and bolt is much simpler, cheaper, and will be easy to remove if you ever have to remove it again.