Best I can do for you
http://www.amazon.com/exec/obidos/AS...ynesworldof-20
http://www.bookfinder.com/search/?au...ic&st=sr&ac=qr
They all seem a bit pricey.
Personally I used a modified form of GDW's "Assault" system, for mass combat, as I was more familiar with it. Don't think it meshed quite as well with the game as last battle did (Damage rules, etc).