I found this thread on another forum when looking up the differences between the MOSFET-style FH020AA R/R vs the Series-style SH775BA, both of which are the same form factor but the SH775 (Series) appears to be a better performer for bikes that like to overheat their stators (kinda like ours)...
Triumph Rat Forum - Series vs MOSFET RR
The basic conclusion of the thread was that a Series RR can potentially draw as little as half the current a MOSFET draws from the stator, due to the more efficient design and the regulating method used. Essentially it seems the Series-type regulates what it draws from the stator based on load, while the MOSFET regulates what it outputs to the battery, meaning that a MOSFET draws all it can from the stator at all times and then wastes it, while the Series draws only what it needs from the stator.
Now this is not to trash the MOSFETs at all (as of this posting I have one on my bike and it's a fantastic upgrade over stock) but to inform everybody that the Series-style SH775 may be a superior RR for our bikes due to the fragile nature of the stator.
So, what's the difference?
Well, they are the exact same form factor as the FH020AA, so if you've already installed one you can swap right out. If not, every bit of information already available on the forum regarding an RR upgrade still applies except you would buy a different model RR. The series type will (in theory, at least, not confirmed by testing on VN750's) draw less current from your stator, reducing the load on it, and allowing it to run at cooler temperatures, which is much easier on it and better for longevity.
Where do I find one?
They can be found just like the MOSFET's, through Roadstercycle, on eBay, or through some other channels if you're looking for brand new. That's $150 or so, I believe. Your other option is to search for a used Polaris 800 Regulator and confirm in the online listing that the item is marked on the top as SH775BA/SH775AA. These can be had for ~$45 or so.
I figure this thread might be of particular interest to those who are considering upgrading to or have a MOSFET on their bike and might like to be less paranoid about stator failure in the future, especially seeing how hard a quality stator for our bikes is to find these days.