I'll put out a few different thoughts. I agree that it's frustrating that some of the parts (freaking heater core comes to mind) are no longer Mopar options.
I think there are some other options. I have purchased numerous parts that are Mopar OEM online. You can get them on ebay,
https://www.mymoparparts.com/, I just bought a mopar radiator on
jksuperstore.com and there are many aftermarket mopar parts websites, I have purchased from many over the past 7 years. Amazon has many Mopar parts as well. So I would disagree that there are no Mopar parts....and again, ebay can be pretty legit.
It's a part by part scenario. Then, look on here (I've actually had better luck going to google and searching TJ forum then whatever part etc, and it brings me to this site and multiple exact threads. If you find the part, like a thermostat, there are credible people that will post an aftermarket that is as good as OEM....or was the original OEM manufacturer etc.
Things like the OPDA, Crown is a great replacement as far as I've read.
You can also go to places like
https://daveysjeeps.com/ that have project vehicles, parts, etc, or keep an eye out for multiple sites that
@Chris has suggested that have jeep parts off salvage TJs. Things like parts you mentioned, spring buckets etc, would be perfect off a part out jeep that isn't a rust bucket.
