Neopreme is a terrible material for seats. Neopreme is not
waterproof despite what some ads say and it soaks up perspiration which causes it to stink after a while. Plus if you get colored neopreme seat covers, the colors quickly fade plus they fade unevenly if they're in the sun much.
One seat belt cover I used to use (until I bought some new seats they wouldn't fit on) was the Bestop vinyl seat cover. It fits like a glove, looks good, doesn't really look like vinyl, and it's 100% waterproof. Mine lasted 7-8 years before I put new seats in.
You sure you want 4-point seat harnesses? If they're not installed with the correct angles, they can cause serious spine compression injuries which killed a very close friend that also broke the leg of and blinded her husband in the same offroad accident. Bad shoulder harness angles and not properly anchored.
Not only that but I have a lot of time wearing 5-point harnesses in aircraft and not only are they terribly restrictive, they are just plain uncomfortable to wear. They're just plain awful most of the time. I think most people that install the grow tired of them pretty quickly and just go back to the much easier to use and more comfortable OE 3-point seatbelt/harness.
Instead, for those times your 3-point OE factory harness locks up, I would suggest a 3" aircraft style lap belt. That's what I installed in my TJ and it works very well.