Where Do I find these 'discs'?

Those are metallic dome switch critters. You can find suppliers on line. Without one to measure, finding the right ones may be challenging, ideally you need to know diameter, height and the amount of force needed to 'click' it. I couln't find any of that info for your device but it is probably available some place I didn't look. You have alternative solutions. The cheapest I found was an $19 replacement non-Jeep remote. Refurbished at $40. Which is comparable to new low end knock-off remotes. An auto dismantler may have one but their price might Not be competitive to other options considering your easiest fix would only need parts from it. Look for a source near you, an example possible source is this Not recommending, just an example. Good Luck! Edit:. These parts are dirt cheap so trial and error might be an option depends on your patience and finances. There are assortment bags and kits but no guarantee the ones you need will be there. Some manufacturers will send samples as well. I Kept looking and found this page with universal repair kits. You might also find folks in the businesses section here that supply them too.