You're not likely to be able to find fabrics that are exactly like your husbands...
You might try searching for pillow panel fabrics, though. Those typically have 18" squares. But since the 18" usually includes some "borders", depending on the design of the panel, you might be able to remove the borders and have left something that's closer to 12". Realistically, probably more like 14"... but that's closer!
You're likely to be able to find some tractors, and probably lots of different animals.