Mate, im sure the ibiza 8v gti uses the same box as the mk3 golf gti 8v, in which case, its the 020 box which is also found on mk2 golfs with different ratios in.
So try scrappers, those internet part finders are good, some will give you a warranty on things like gearboxes, or try a vw salvage firm, loads advertise in the back of vw magazines. Have a sneeky look while in the newsagents!