Jon
These are available in the states from jg airguns...see their excellent website.
The first price you get will include a silly amount for insured and tracked postage, but if you email John back and ask if he's willing to post at your risk - the cost becomes reasonable (if you're willing to take the risk) - this is what I've done a few times in the past and it's worked for me.
Hope that helps if you can't find something here....
Harvey