I think you are better off getting the kids bag and just tuck the extra length under him. Alternatively at two, you might want to just use a bag wide enough bag that both of you can sleep in it. That way you can better track how he is regulating his body temperature.

Be careful about about straps on any sleeping equipment for a toddler. They can very easily get wrapped around their neck. I think a better idea would be to have a bag that cinches around the neck (not tightly!).

I have a denim fleece lined bag my mom made for son about that age. You are welcome to borrow it, but I don't think you are very close to LA.