Le Quack:
If you look at my webpage, you will notice that I doubled with a Ti-Sapph laser, which is a pulsed 795nm laser. Therefore, you should be able to grow your own KDP crystal and double it in a 808nm laser if you have a powerful enough laser.
Wolfman 29:
The best reference for you to look at is reference 9 in my full report.
Electro-optic, linear, and nonlinear
optical properties of KDP and its
isomorphs
D. Eimerl
This paper discusses the theoretical limits of frequency doubling with different types of KDP-like crystals. He shows the limit for type 1 frequency doubling for KDP at 1064nm to be an input power around 500mW (Figure 30). Different isomorphs have lower treshholds and type 2 frequency doubling also has lower threshholds.
If you read Wikipedia about Green Laser Pointers, you will find them say that the green laser pointers have a pump laser at 808nm between 100-300mW. The threshhold for this case and type 1 frequency doubling is 300mW and type 2 frequency doubling is 40mW. They could also be using KDP*, a purer form of KDP, which can also decrease that threshhold.
Hope that helps.