Get on Craigslist or check out the classifieds here. It seems at least 75% of new Wrangler owners take off the stock tires/wheels and sell them cheap. The used 2010 Sport I bought a couple of months ago had takeoff rims/tires from a Sahara on it. The tires were pretty well shot and I found a set of five 255/75/17 tires and rims for about 1/2 what it would have cost me to buy 4 new tires. Tires had about 3000 miles on them.
I have now have 5 nice allow wheels, 4 worn tires, and 1 tire that has never been on the ground I'd sell cheap. Even if I gave them away I'd be money ahead. I'd bet you can find something bigger, with allow wheels, for less than buying bigger tires on the wheels you have.
If you do decide to stay with those rims I'd stay with 265/75/16's. That is what I have on my Tacoma. They are 1/2" shorter and about the same width as the tires on my Wrangler. Not enough to worry about.