chestnut,
Frist, I would try George Anderson.
Then, I would try Scotty Benedict:
Pre98 Vintage Militaria and Collectibles
Then, I would try Simpson's:
Luger Assessories to see what they have.
Next, put a WTB (wanted to buy) add on this site.
Finally, try ebay but be sure to read this:
Luger Grip Fraud first.
If you find something, I know the good folks will give you their opinion on them.
Richard