Saturn ball joints
 

Those DRY nylon front ball joints.

Can you inject grease into them ? They sell a needle with a grease gun
nipple at the end to inject grease into rubber cup that keeps dirt
out. I would think that grease would not degrade the nylon (or
whatever plastic) ball and socket (maybe the ball is metal and the
socket is plastic-I don't know) I would think that if grease can keep
metal ball joints from wearing- why not grease those unserviceable GM
ball joints. If regular grease degrades the nylon, do they make a
grease that doesn't degrade it?

Can you get aftermarket ball joints with a grease fitting on it?