That's a pretty heavy-duty rig.
I recognize some of the fittings - it looks to me like somebody adapted:
-Small Garden Sprayer
-Ball Valve (like shut-off for cold water under a sink)
-Needle tapered-down / adapted to fit
(Probably a football inflator ground-off at an angle - these treads might fit into the valve)
I'm not sure if it would develop enough pressure for serious injection - a while back, somebody (Bryan S.?) posted one with pliers-like grips that you squeeze to pressurize. THAT one looked like a better idea, IMHO.
If you only use one once in a while, the cheaper regular syringes / clean veterinary-type syringes with relatively large-guage needles should work fine.