I recently received one of these cases as a hand-me-down from a friend to replace a competitors product that I had been using since 2011. The only seller still offering the "upgrade kit" that I've been able to find is in the UK and won't ship to California. I have been scouring marketplace websites for a while with no luck. I've read rule #14 and wont ask that but does anyone know any source where I can buy these in the USA?