Most little parts are the same as any T series diff, so you can actualy just walk into Repco or some place and say you have a T-18 or Celica or Corona etc. That will be good for buying pinion seal, or a diff rebuild kit containing side bearings, pinion bearings, pinion seal, pinion nut and maybe the colapsable pinion spacer.
Alternatively, the bearings have a number on them and you can get the same from any industrial bearing shop.
But if it has a whine, you only have a slim chance of fixing it with new bearings. The crown wheel and pinion would probably need to be replaced, and installed by a mechanic. You can buy this from Toyota, easier if you have the part number handy. Someone here will give a part number if you know what ratio you want.
Or get a good second hand gear set.
All overhaul parts are available from Toyota.