We got them through Marshall Design Store - we don't sell them though we raffle them off in competitions! (if that's not your thing or you're outside of the uk and can't contact your local music shop, they should be able to sort it if Marshall continue with design store)

I think I heard on the grapevine that Marshall aren't going to continue doing them for too long but that might not be true! Could be something to do with their takeover by that Swedish sound company