Aftermarket carb for cateye

hey all i have a cateye 49cc and i am looking to upgrade the carb with airfilter. where should i look and how do i know im getting the right thing?

Go to scooterparts4less and click on the picture of the cateye at the top of the page...it will bring you to a page to everything they have for a cateye including hp carb /manifold,velocity stack and intake setups.................Peace