Hi there, so sorry for your loss

You did the right thing by reaching out here.
I got my first panther cham in 2021. I hadn’t kept a chameleon in YEARS and there was definitely a learning curve (believe it or not, it gets better!). I got my boy from Fram‘s Chams, so he was very healthy right from the beginning. I got him at the very end of July, so.. between August to mid October, I started to notice him closing his eyes during the day. That’s definitely not something you want to see in chameleons as they don’t sleep during the day at all. Turns out, I had been using the wrong multivitamin (it only had beta carotene in it, no preformed A vitamin. Common mistake), but that wasn’t the whole picture. Earlier, I had run out of feeders and bought some emergency crickets from Petco. In only a couple of days after feeding off the Petco crickets, the runny poops started. My cham’s eyes stayed closed even after I had bought the right multivitamin and began supplementing with it. Turns out he caught coccidia from the Petco crickets, and it was a nightmare to clean up. Issues with supplementation come up a lot, but any time you see eyes closed during the day, you‘re going to want to rule out parasites.
If you are still feeling like you’d like to try again with another chameleon, I strongly recommend thoroughly sanitizing the cage you had this little guy in, and tossing all the branches/vines/plants that were inside of it. Basically, if it isn’t a plastic or metal surface (and even plastic can be porous), get rid of it. Bleach won’t kill the coccidia oocysts, but 40 volume peroxide will. You can get it on Amazon or from any beauty supply store (it’s used to bleach hair). You’re going to want to empty the cage out entirely, take it outside and spray it down from top to bottom in 40 volume peroxide (inside and out). Scrub the frame, and wipe the mesh down with soapy water after you spray it down with the peroxide. let it sit for a week or so (not directly in sunlight. Bringing it back inside during that period is fine), then repeat that same process a second time. Goggles and gloves are a must because you definitely don’t want this stuff on your skin. Should you determine that this is entirely too much work, you can get a new cage. If you plan to keep your new chameleon’s cage in the same spot, I’d wipe down the surface the cage was on with the peroxide as well. Don’t re-use anything you had inside of your sick chameleon’s cage! if you used a wet vac to take care of all the water drainage, toss it or use it for something non-chameleon related (coccidia oocysts love water, and a wet vac is going to be next to impossible to sanitize). Coccidia is so difficult to get rid of, and as you have no doubt learned, it can also be life threatening in chameleons. After this experience, you definitely won’t want your new baby (if you get one) to get sick with it as well. I didn’t even keep the same temperature/hygrometer probes, I just replaced them all.
Buying from a pet store, chain or otherwise, is always such a gamble. There isn’t any telling where they source their animals from, nor do you know what condition they’re in by the time they arrive at the store. Parasites in store bought chams are unfortunately very common. I’d call around for an exotic vet willing to do a sample on your next chameleon before bringing it home. That way, you know exactly who to go to if you get a new baby and notice that anything is off. Fram‘s Chams, Ipardalis, Chromatic Chameleons and Kammerflage Kreations are all reputable breeders (and there are certainly more, those are just several I could think of off the top of my head).
Again, I‘m so sorry for your loss!