you can either get EPDM or Nitrile material o-rings from a bearing supplier pretty easy...
Main Jet: 1.2mm cross-section x 3.5 mm ID x4 (if you cant get these, i managed to get a 2x1.5 to stretch over the jet nicely
Float Seat: 1.5 mm cross-section x 5 mm ID x4
Float Bowl Drain Screw: AS568-009 (7/32″ ID x 11/32″ OD); Metric dimensions: (CS 1.78 x ID 5.28) x4
Fuel line T-piece 2 x 8mm x8
Carb bowls: 2x68mm X4
good luck

BTW, these i got for my 550...