Piston rings differ depending on the year.
CG10 & CG13 use the same rings up until 07.2000, (12033-99B20), then they go to a different set of rings which are impossible to get, (12033-1F700's), been there done that and opted for another option. There were different rings on the VERY early engines but I don't know of anyone with one of those engines and cannot be bothered to find it in the parts list since it's not relevant to your CGA3.
CGA3 use different rings, 72mm bore v's 71mm bore for the CG10 & CG13. As for the rings, I am sure Frank said something about them being a tad thinner then those on the CG1x engines......I'm sure he'll post up his findings and some pics, as he's had more of these engines apart than most of us 
As for uprated rings, not sure to be honest......you having problems Paul?
I would say the best bet maybe to start with Matt Humphris but I suspect if you cannot find any from any ring manufacturers than you'd be looking at a different piston, which is going to cost ya
