As I work in North Africa and live in Houston, I do a round trip every month through London. In the past six years I've carried auto parts to people on both sides of the pond. My wife thinks I'm nuts, but it's not a big hassle, and it's enabled me to meet some interesting car nuts.
So, if anyone here is interested, I could possibly carry over small shipments of this glass (1 or 2 pieces, maximum). I would only ask to be reimbursed the cost of repacking (if required) and the UPS/DHL/FedEx costs of transhipping to the final destination from Houston.
I doubt that this glass, well padded and packed, would still be small enough to qualify as carryon baggage, so it would have to go in the checked baggage hold. This may be as, or more hazardous than shipping it normal commercial air freight, but the offer stands if anyone wants to try it.
John