I really do appreciate the replies. Thanks.
There is a reason I was looking at standard Pistons. But first let me give a bit of history on this ski. And sorry for the length. I am bad at keeping things simple and to the point.
I bought it 3 years ago as a project just for the fun of rebuilding something and making it run. I had no idea if I was ever going to use it or not. Turns out it was a lot of fun and I was having a blast on this old tippy and fun machine. This is what I did.
1) replaced the crankshaft with an SBT rebuilt one
2) had put in 2 WSM Pistons, rings. Tested the cylinders and they were within spec, l lightly honed them myself and they cleaned up really nice
3) cleaned carbs
4) replaced oil
5) tested the injection pump to be sure it worked. It was OK.
6) replaced the in tank fuel lines that rotted away and changed the filters
7) brand new CDI box (had no spark)
8) did some minor work on the hull
After the rebuild and break in I was getting 145 PSI on both cylinders. I used it for 1 year and after that year it still had 145 PSI on both cylinders. So I was quite pleased with myself.
After that I decided to take care of somethings I should have done before.
1) bought a mikuni carb rebuild kits and did both carbs. Was working like a dream after that.
2) reupholstered the seat
3) bought a choke cable
4) bought a blacktip handlebar cover (she is looking pretty snappy now)
And now halfway through year 2 of using it the engine died (year 3 of owning it). After pulling the engine I discovered why. The nut that holds the oil injection cable into the oil pump came loose and detached. So no oil and there goes the engine. So when I rebuilt the carbs clearly I did not properly fasten that nut when I put it all back together. I have dismantled the engine and the PTO piston and cylinder is badly scored, the mag piston and cylinder looks good.
So these are the options I was considering.
1) buy a used cylinder that was still usable and standard size to go with my one good one and replace both Pistons and rings. Seems a little sketch I know. But it was the cheapest.
2) Cylinder exchange program with SBT or Full Bore. Potentially the more expensive option but also the easiest and probably the most reliable of the options.
3) Take it to a local machine shop that does not specialise in 2 stroke Rotax engines to have them Bore it out and home it to the next size up and buy Pistons to match with it. I am worried about the lack of expertise when it comes to Rotax engines in my city. So this leaves me with option 1 or 2.
That's my story in a nutshell. lol...