Inductive pick-up coil

Need help on an inductive pick-up coil. Building a robot that basically will follow a buried wire. Need a coil pick-up sensor similar to what is used for an invisible dog fence, or some of the robotic lawn mowers that stay with-in a given area, or some of the automated transporters used in warehouses. I have looked at several parts catalogs and just haven’t been able to find what I want. --- Suggestions for a low cost DIY coil idea that I can build, or buy and tune, and be able to work with? --- Thank You

some sort of hall sensor could sense the field around the wire?

How about a Fox and hound tool like this one. It puts a signal on the wire and the receiver makes a tone that gets louder as it gets closer.

https://www.mpja.com/Cable-Wire-Tracer-Set-with-Clip-Leads/productinfo/31866 TE

I think you can get them cheaper than this.