Did you try and contact someone at Murrays? I would think either they would know or know someone who would.
Also try Mark Mitchelson at http://www.sailingproshop.com
They often get used Sol Cat parts and they might know.

[color:"red"] UPDATE: [/color]
[color:"black"] [/color] There is a listing for the jib in the Murrays catalog (part# 30-6112 $335-$470) so I am sure someone there could give you the correct dimensions.