Your question makes no sence, There are litterly a shit ton of different tires for a 15 inch rim, all the way from 29-whatever you want. The reason that they went with a 15 is the tires are cheaper for the most part. Going with a 15 instead of a 17 or 20 gives you much more sidewall to play with. As well as a more comfortable ride.

What you should be looking for in a tire size is 31-11.5/15, 32-11.5/15 33-12.5/15 and so on.

If you are bound and determined to get a larger wheel, I have a set of 5 OEM silver alloy XE style wheels that are for sale. $150.00 gets them. The only reason that they are for sale is that I went to a 15 inch wheel from an older pathfinder.