I'm not having much luck finding a part number that makes sense. One diagram shows it as the float check valve, another calls it a solenoid valve, and another calls it an idle jet. If it's an idle jet, the carb kits you bought should have replacements. If it's the check valve, about your only hope is to ask around here on the forum, try a marine bone yard, or check ebay for parts. You may need to buy the complete used carb, but that's not necessarily a bad idea.
Be aware that you should replace the aluminum crush washers after removing the fuel lines. Those are one use items and not replacing them may result in you over tightening the banjo bolts to stop the fuel leaks.
