Your gun has a 5" barrel. I knew from your photos that you had a long barrel gun. Top-break's with a 5" or 6" barrel are scarce. You made a real good find for $140.
As for the grips only a few ideas come to mind. The standard grips for your gun are almost always the black hard-rubber with the S&W intertwined logo. The frame of your gun is a round-butt.
You could try looking at gun shows. It's possible you might find someone selling an original set of grips or might be able to find a junk gun you could buy cheap and take the grips off of it and put it on your's.
Another place to try is ebay. Just type in Smith Wesson Grips and look to see what's available.
The last idea that I have is Numrich Gun Parts. Here is their address:
http://www.e-gunparts.com/. Numrich is where I get my parts. Word of warning about grips. There are several variations that can fit your gun.
Here is a picture of the correct grips for your gun:
There are a few reproduction grips available on ebay but I can't tell if they are for the small-frame .32 or the large frame .38.
Mother of pearl grips were a factory option on guns. Pictured below is my .38 Double Action 5th Model with a 4" barrel. My gun is completely original and I have the factory letter certifying it.
jsmith