To be sure I've got the right one, is this it?
http://www.fleetalternatorstarter.com/alternator_10352.aspx
40A, internally regulated? There's probably one out there, but finding it would be a job for an auto electric shop.
If close would do, take a look at a Lester number 14684. It's internally regulated, 55A, and I'm pretty sure it's the same frame.
http://store.alternatorparts.com/14684n-55-amp-nippondenso-denso-type-alternator.aspx
This was the 1st good image I found; it's available much cheaper if you search for it. As the adv says, it fits Chevy Sprint, Suzuki Samurai, etc. Should be available from any bigger auto parts chain.
The image shows the B lead clocked 90 degrees off from yours, but it can be re-clocked easily. It also shows an extra brace on the fixed side pivot, which can be removed when the B terminal is re-clocked. The only thing I'm not sure about would be the 'extra' terminals. For most of the built-in regulators, you just need a jumper between two of the terminals to turn it on. Most can't be turned off, once they are up and producing power; probably the same for the one you have now.
Try this site & you might find an exact match:
http://www.psep.biz/store/denso_alternator.htm
FWIW,
Charlie
Followup:
http://www.ase-supply.com/Denso_Alternator_100211_1680_p/nd-100211-1680.htm
Search for Denso alternators with part numbers starting with 100211-xxxx