Hi Mata Hati
I would think a knit using say stocking stitch would definitely use less wool than say cable, but not to the extent you need ! If you can't get hold of the more of the same shade of wool to make up the jumper using aran stitches etc, why not introduce another complementary colour of the same weight instead, to make up the difference. As you are now familiar with the pattern, you could incorporate some colour bands either vertically or horizontally (the latter would probably be easier). You should make up the back and the front at the same time (obviously you would need two pairs of the requisite needles), so you don't run out of your major colour before you have finished one part.