A S&W 625 is a blast. I have the JM version but any will do.
That seems to be the logical choice if you ask me.
The O.P. want s a large frame, and already has a 45. Not having to keep another calibre on hand is nice, and .45 acp is pretty reasonably priced. Also the model 625 is reasonably easy to come by.
The other sensible option would be the a 610 if you can find one, as it can fire the .40 S&W the O.P. also aready has on hand.
There are a TON of N frame S&W aftermarket grips available in wood, or any other material you can think of.
The GP100 is also a great gun, but 1. It's not a large frame. It's a mid size. 2. Not a lot of selection for wooden grips. There are a few, but you're fairly limited.