I noticed that this forum is pretty much dead, I'm no kymco mechanic however I am a Harley tech by trade, I have pulled the carbs off of the ol lady's venox and I do know what screws you are talking about. The best place to go to replace them is going to be a place like fasten all. I have a place by me called Conroe Bolt and fastener, I use stainless steel to replace most hardware as I hate rust.
On another note if you are planning to jump your bike with a car don't turn the car on. The amps that a car alternator puts out can fry the charging system on a motor cycle. Just leave the car off and hook up the battery alone should be plenty to jump your bike. Good luck.