Go online and search for Ferrari parts.
I found a 550 windshield for $1,000 last year,
http://www.ferraripartsexchange.com/
(there's no guarantee of course that they also have a 456 windshield)
In my case, I bought OEM glass for less than half price (with a slight blemish, ala discount). I paid for it in cash (which State Farm will reimburse when I finally need to install the glass). Right now, the glass is still in a crate and sitting in Sacramento, waiting for me to call to ship for installation. Until then, I'm defying any rock on the highway to chip my 550's glass...and each time it happens, the local Windshield Doctor says, "The more the better!"
I keep the payment receipt in the car, in case I get some cop with a bug, wanting to ticket me for a cracked windshield. (considering I turn state troopers into the U.S. Atty for civil rights and state law violations, they're gunning for me)