The CB750A shares clutch parts with the Honda Civic car from the early 70's.
I have found these for sell in "sets" from transmission supply houses; although the necessary quantity didn't always match.
So, if your motorcycle parts source doesn't have them (or says they can't get them), search for Honda car clutches. The part numbers will match.
I found this fact by internet sources, and I'm not the only one:
Fibers and steels? Available in rebuild kits for late 70's Honda Civics with the 2 speed automatic transmissions. Yes they interchange. Also less expensive than the bike discs. The car rebuild "kits" have fewer discs than the Hondamatics take. There are a lot of suppliers out there for the Civic transmission parts. Here's one that I've used.
Here's where I got them from in Sept. 2012.
"We can get these for you separately. The frictions are $1.93 each and the steels are $5.25 each. We will have to drop ship them from the manufacturer, freight should be about $10.00. If you would like to order them let me know.
Thanks
Julie
Julie@Makcotransmissionparts.com
Hope this helps. 
If you have a high mileage Hondamatic 750 or are rebuilding one for more performance, replacing the clutch discs and steels are good insurance when your block is split for bearings/etc.
I can't find an internet listing for D&E Automotive Products. Alto has a web site showing distributors in the USA, none in the northeast. I emailed an inquiry to them that wasn't responded to.
The cheap source is still out there. $1.85 each is very cheap until you add the $99.00+ shipping charge when I tried to buy 10 of each.
Speaking of getting 10 each of the discs/steels, you only get 8 of each with the Civic overhaul kit. Makotransmissionparts.com has allowed me to buy more of the friction discs at $1.93 each and the steels at $5.25 each with a reasonable shipping charge direct from their supplier.
Yes, the car and bike discs interchange. Your local import transmission rebuilder may have sources that we don't. Just an update for these parts.
Jon Weeks
