Hi JMJ,
The most common carbs here in the states are Walbros. The 25cc engines run best with 11mm carbs. The smaller engines may like a 8 to 10mm better. The 40cc can use a 11mm, 12.7mm or a 13.49mm. I am goung to try a 12.7 on mine, but I'm sure that it would run just fine with the 11mm or 13.49mm. Just about any two needle Walbro carb of the above sizes will work fine. You should be able to get some good deals on E Bay or RCU classifieds. The venturi size is what you are concerned with. This size is cast into the venturi enterance on Walbro carbs in 64ths. 28/64ths equal 11.1mm. Some models have have builtin choke and others have a builtin promer bulb with an extra fuel connection. I don't have any idea of how much thw taxes would be. I know that you folks pay a lot up there. I like the WT-324 for a 11mm carb because I bought several new on ebay for $30. Good luck.

Dave