If you're real stuck, you could try these guys in UK. I've no idea who they are or if they're reliable btw - I just happened to notice it on ebay.
http://www.ebay.co.uk/itm/toyota-supra-gearbox-/220952118234?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item3371c5c3da#ht_964wt_1196