James,
You were so close .........

You can actually look up the parts on the Nth American site of New Holland. So if you start with the link
www.newholland.com and follow the path via Nth America --->Seach for Parts ---- Model number ---- > part name or number, you will come to what you need,
(I was going to paste a link to it here but it isn't possible after searching for the parts.)
Anyway, if you follow the path you'll get there. Once there, you can choose on the right hand side to have the TAB showing FIGURE or PART SEARCH. Closet I could get for the moment is the Figure Diagram of all the transmission parts. Shows the cover to the brake area you have already removed.
Try it and lets know your outcome.
Regards,
Rick
EDIT: It doesn't look like they are available from New Holland anymore. I don't know if you have tried
www.bare-co.com but I can't see the steel disc there, only the linings.