The purple gene is usually dominant, especially in indicas, so if either the male or the female has the trait for purple buds, the progeny will produce at least 50% purple budded plants. As far as purple genetics you can use as stock, there is plenty out there.
Chimera's Mental Floss and Ace's Pakistani Chitral come to mind immediately, but there are many breeders out there with beautiful purple genetics, and many strains that are not considered purple will often have a few purple phenotypes or tendencies.
As far as picking out a purple male, it shouldn't be hard, you should be looking for something like this.
http://27.media.invalid.com/tumblr_kz4tmokBjL1qadflco1_500.jpg