Hi,
The belt I used for my +20mm pulley (will check belt later) was 5PK-1055 I got it from Repco...its a standard belt for a Ford or Holden or something. Find a machine shop to do the work. As I knew the guy who did mine, I got a cheaper rate BUT even normal rates should be a LOT less the $550! I needed a smaller idler pulley too, that was the hard part. Though you will find one if you're creative enough at maybe a wrecker or buy one from Fensport.co.uk or dare I say Nevo (I asked them) for a rather nasty $145.
It took me about 4-5 hours to put the pulley on and replace the belts. You have to undo the engine side engine mount so you can put a rattle gun on the pulley bolt!!