If you're lucky enough to get your hands on one of the 100c Minarelli engines but want more power, here ya go!
Malossi offers this nice cast iron cylinder kit in 57.5mm. That means its about 124cc! 14mm wrist pin on the piston. Malossi claims this will work with the stock head as well.
Malossi part number 3111374
Comes with cylinder, piston, rings, pin/clips, gasket set, and new reed material.
Fits the following models and likely more:
Aprilia Scarabeo 100 2T
Benelli K2 100 2T
Italjet Millenium 100 2T
MBK Booster 100 2T
MBK Nitro 100 2T
MBK Ovetto100 2T
Yamaha Aerox 100 2T
Yamaha BW's 100 2T
Yamaha Neo's 100 2T