The bras for the XK8 are usually sold as 2-piece sets. I have one (2 pieces) on my 2003 XK8 coupe. The label says Part # C2S 4496. I bought it at the Kansas City Dealer (Aristocrat Motors) for about $140 in Mar 2007. The date on the label is 10/27/05.
You might try Classic Jagguar Parts in the UK. I can't find the business card but they advertise in the Jag Journal.
Dave Belanger - Houston
Dave Belanger
Jaguar Club of Houston
2000 S-TYPE 4.0
2001 S-TYPE 4.0
2003 XK8 4.2 Coupe