I sold my OS carb a while ago otherwise I'd sell it to you. I had a guy turn down a .21 Nova Rossi carb to fit mine and that really woke it up! If you're going to buy another OS carb you might want to see if one from an .18 will fit on it as the block boss throat is 13mm if I remember correctly.
We can run any size carb that we want as opposed ot the car and truck guys as they're limited by ROAR rules to a 5.5mm carb bore.