Surprisingly, a lot of manufacturers have used 28mm PWKs for stock carbs on 80-85cc dirt bikes. If you search ebay for "kx85 carb" "CR85 carb" "YZ85" etc. you can find them easily and sometimes for very reasonable prices. Very minor differences between an OEM and the aftermarket versions. The important thing is look for the carb cap to be held on with two screws, not a screw-on like the stock blaster carb. That is a Keihin PE carb.