Wheels with proper backspacing are best, but if you can't do that just get some SpiderTrax and call it a day.
They mount to the stock wheel lugs, and then you mount the wheels to new lugs that are on the SpiderTrax. You can see it here
For that reason, they're technically not "spacers," they're really "adapters." True spacers--which just go over the stock wheel lugs and leave you less lug to hold your wheel--are super dangerous. I'm not sure anybody even sells those anymore. Somewhat oddly, most folks use the term "spacers" when referring to "adapters".
There are some companies besides SpiderTrax that make spacers/adapters, but SpiderTrax seems to be the industry leader. For the Wrangler, they make 1.5" and that's it as far as I know.
You've just got to make sure that you check the lugs--both on the wheels and the spacers--a few miles after the install and then at each rotation thereafter.