We make our own probes.We go to a junk yard and ask for the (spring steel) for the trunk of a large car.(no imports) the steel is to thin.You have to have access to a wielder or know someone who welds.Trunk steel comes in 2 pieces.You have to straighten it out and make a straight rod from it.One piece comes out to about 5 foot.once the piece is straightened out you need a small piece of hollow pipe for the handle preferably 6 inches.Drill a hole in the center of the pipe but not all the way through.Then you weld the pipe to the rod.All most done.Next you need to put either a bolt or a little bit of wield on the tip of the probe.We use a round dermal tool bit because it is harder then most other material and lasts much longer.The It should be just a little bit larger then the diameter of the rod.This makes it easier to probe.less resistance.Thats it.it sounds like a lot but it is easy.But you need a welder.
Or you can buy them on line. 30 to 40 bucks I have seen them go for.To make one it will cost you 10 to 15