I know this is an old thread but you probably get better responses here. I used to frequent the site often. Love the P64. Also there used to be a place that made custom stocks from wood in Central America I believe. Can’t remember the name but the site would know. You can also get some specially made with extended grip to accommodate the pinky.
http://www.p64resource.com/forum/viewforum.php?f=1&sid=10680f7077c34930ca5c69d42844e983