Get a piece of any old cheezy steel rod of suitable length, probably about 4 feet for your purposes. Pound a small flat like a spade drill on one end of it. Make darn sure the end is BLUNT, so it won't cut the pipe if you hit it.

Chuck it in your cordless drill (and take an extra battery), and start off down the path of the pipe. Every so often, drill a hole in the ground and see if you get mud on the blade or water coming out.

I've traced leaks and found the end of water-drilled holes etc with that method. Goes pretty fast, beats heck out of pounding and pulling, or digging.

I'll warn you that underground, water can take some odd twists and turns. I've had it come out of a hole 40 feet from the pipe in a case when I didn't know where either the leak OR the pipe was….