Paintballers!!!  Make your own paint grenades.  There are write ups on the internet on the filler and tubes.  i used silicone tubing from home depot in the plumbing section and fashioned my own pin and retainer from mechanic's wire.  here is the filler station

unscrew the top, add your fill.  attach pressure hose to top nipple at approx 30psi.  cap one end of your precut tubing and slip the open end over the bottom nipple.  hold tight, open the valve and fill to your desired capacity.  play with the size of the grenade and seek which is best for you to carry and throw.  works great.  pretty awesome station, especially when i can now make as many as i want, instead of cringing at the thought of $5 minimum per grenade at the field!!