You will need:
5/8 inch clear vinyl tubing (should fit in 1/2 inch pvc with some cramming)
Hot glue + gun
At2k
Tape of your choice
Dremel
Screwdriver
(Some pics are courtesy of Uncle Hammer)

Stock At2k. Open it up, fools!

Internals of the At2k.

Don't lose that o ring!
I don't think you need a picture for this, but cut your pvc to four pieces of seven inches.

Now carefully pry the stock barrels out. cutting leaves a ring inside that we don't want. Your turret should look like this when you're done.

Now take your clear vinyl tubing and cut one inch segments. I think everyone hear can imagine four one inch segments of this stuff.
Sorry I don't have a pic for this step, but cram the clear vinyl tubing halfway into each piece of pvc. then insert the other end of the clear vinyl tubin into the holes on the turret.
Add tape to hold the barrels together, plug the pump if you want, and close it back up.

Isn't it glorious?