Ebay. I just bought some for $16 each shipped . The ez start you can pickup cheap there too. Used carbs were the same price. A cheap china .18 sell for $70. The .15 is to small. I have some .15 in t maxx and they are slow. The 2.5R is ok but the 3.3 are expensive now $125 just for the block...
It's best to find a New short block and put a carb and ez start on than mess with used parts. Costs around $100-125 for a whole new block engine . I have refurbished 3.3 engine's that have had a giant hole's on the bottom. I used a small thin sheet of aluminum to cover the whole's and JB...