I own, and use, the Project 1. I got a Scot Hendryx SB-1 kydex sheath for it and it's proven to be a pretty good purchase. This is my first real experience with kydex, so there may be better, but this one meets my exacting standards.
One thing, if you got your knife for collecting or you want to keep it in mint condition, be warned that kydex will cause a bit of wear on the kalgard, mostly on the spine. Not much, just some thin streaks, but it will rub some off with use.
Gun people call this "holster wear" and tend not to obsess about it.
Likewise, though the kalgard is nice, it's not neccesary to keep the blade from rusting with reasonable care. I don't oil or treat my knife in any way other than to clean and dry it off after I'm done with it, or rinsing it in fresh water after it's been in salt. I have had no problems wit the steel at all.
I live in Florida, which is humid and has a lot of salt in the air to begin with, on top of that I spend a lot of time in swamps and estuaries. So I know what I'm talking about.