I'm not sure about a lefty youth model. I'm lefty myself. I got my grandson a Savage 11FYCAK in 7-08 with detachable box mag and muzzlebrake. What a shooter. The first time out after sighting in and breaking in the barrel shot groups from .41" down to .29". I was impressed. He might not get it.
You can always get a Savage with the wood stock and have a competent gunsmith cut down the stock for a shorter lop then get a replacement later when your son gets older. They make the models 10, 11, and 16 in left hand.