I have been chasing a freon leak for a couple of months and recently found a leak at the low pressure port by the firewall. Finding the correct replacement Schrader valve has been a challenge. Even the local Jag dealer ordered the wrong part ( of course no returns). I did some research and found the the correct valve is Schrader #8089000070, 8mm x 6g core. Its a larger valve core than most. They are sold by Rock Auto under part name and number, Four Seasons #59335, $1.02 each !! The dealer sold me the WRONG part for $14 and change. You will need a valve core removal tool that you can find on Ebay for $5. Make sure to buy one capable of fitting an M8 valve.
Good Luck