A few quick pointers from the other nother side of Oz .
If it's a PW 50 and you have a discernable lip at the end of the ring travel you need to go for either enough oversize to correct or replacement barrel.
(1mm lip on a 41mm piston = massive ovality / piston knock) which will inevitably cause the ring to shatter and lunch your bore.. Other prob is that 2 smokes can tend to lean off as top end compression drops off often causing them to scream for the last few rides just before they shit themselves!?
Right now Ebay is you biggest friend using your international search and looking at USA parts should turn up a variety of options for you.
Cost to re-bore / hone your barrel is about $100 unless you know someone.
Top end rebuild inc new piston,rings , top end gasket set , gudgeon pin / brg and clips should be under $200AU on your door.
(rd350 twin using genuine Wiseco parts = $240AU shipped)
Might help mate
Now that's cheap!
