maybe put two on a 4x6 image, print them at costco or sams club for cheap, then cut the 1 inch strip off the bottom and cut the two pictures apart. that would probably be the cheapest way.
or, does it have to be 3x3? maybe enlarge/crop to wallet size (3.5 x 2.5)
or, in a photo editing program add a digital frame around it so the whole thing is a regular size, but the photo is still 3x3?