Try your local irrigation supply, plumbing supply, or big-box home improvement. I think the small brush you're referring to may be a plumber's brush used for cleaning copper prior to soldering (at least that's what we use for cleaning metal threads). Other things you'll find handy are PVC compression couplings and tees, 2 pipe wrenches (14 in.), a pair of slip-joint pliers ("water pumps") and pipe dope (teflon tape or paste). A lot of old systems around here are also galvanized - we convert to PVC when and wherever possible, using male or female adapters or compression.

Your best bet is to dig down at the next head in line and follow the connection to the pipe and check the direction from that point. You will also get a feel for the length of funny pipe the heads are probably on.

What type of sprinkler head are we talking about?

Of what level of incompetence is this plumber? I assume we're talking about lawn irrigation and not fire sprinklers. Gray pipe is almost certainly sched 80 pvc. It's harder to break but this clown did it and it's not that hard to find. Maybe he should call in professional help.