Best reg/rec replacement for early M900?

My reg/rec has been on the way out for a while now, and with spring on the way I'm looking to get a few things sorted on the bike - this being the main one.

I read a while back that rather than just replacing the standard (and therefore still eventually prone to failure) unit, there was a newer/uprated one that was a direct replacement?

Anyone possibly point me in the right direction please?

It's a 93 M900. Also is it a relatively easy self-fix job?

thanks
ed