First, I don't own a MK23. This is just based upon what I've seen online, and what I've seen on local fields.
I've seen them mostly carried in something like this: http://www.redwolfairsoft.com/redwol...il?prodID=9069
First thing that came up on Google, right there, lol.
Uhh, I've seen guys carry them in M4 mag pouches too, or they just don't have a holster for their MK23's, as they use them as primaries.