Visit the Team Iceshanty Proshop
You can use a number of things for a spud bar. they also do make ones specific for ice fishing, run a google search for ice fishing and spud or ice chisel and you ll find what your looking for. go to any Gander or Dick's or any local bait shop and they should have them as well. To use it you just give a few good whacks on the ice in front of you as your walking out. If it goes though, go no further. also your looking to hear the sound that is made as well as you hit the ice. A nice dull thwack is a nice sound when your spudding, means good solid ice. Also is your spudding your way out and see any pressure cracks make sure to whack and those to make sure they are solid. Where In NY are u from?
Don't always rely on the spud going through to tell you to go no further. Two weeks ago I was checking bait traps and spuding as I was going along and the spud was not going through. And I was really putting it into the ice hard. It wasn't going through, got to with in 4' of my bait trap and as I was checking the ice the spud didn't go through, stood there a while then I went through.