Thomas Knight Turbos use to make turbo, twin turbo, and supercharger kits for those engines. I have not talked to him for a couple years however. Geoff, the owner, is incredible helpful.
You also might be able to find more K-Series engine info on www.probetalk.com.
I use to have a website that was specifically about the Mazda K-Series engine, It and all the content are no longer however.