I tried using Valve's prefab but it only let me take one Combine ball out then shut down unless I placed the ball back into it in which case it would spawn another one. Repeating this process resulted in tons of Combine balls that would just float around my level. I have since fixed this multiplier problem by modifying the prefab to spawn one ball after the previous one had blown up. I also was able to prevent the balls from being placed back into the dispenser once it was taken out. When fired back at the dispenser they now just deflect off of it and continue to ricochet off the walls until they detonate, thus respawning another one. I couldn't ask for a better result. If anyone wants this modified prefab, i'll add it later today.

? quoting ReNo

Might be cool to add this to the prefabs section right here actually mate. Good job fixing it...even though I personally didn't know it was broken

Great, i'll add it to the prefab section today then.

Well, Valves original prefab would only let you take one or two Combine balls out of the dispenser and wouldn't spawn any more. I just tweaked it a little.