Just take 5 yards of jersey cotton knit and cut it to about 65 cm wide - there ya go! It won't ravel.
However, if this is for the little cutie in your siggy, I wouldn't recommend a stretchy wrap as he looks like he is probably heavy enough to get some serious sag. A woven wrap would be much more comfortable - I some info on them in my siggy.
the one in my siggy is just 6 yards of cotton gauze, split down the middle lengthwise.