[Boatanchors] somewhere there is a mountain of probes of all types rant ---

[Robert Nickels]

When it comes to gaussmeters, the probe essentially *is* the 
instrument.  Unless you're looking to make research-grade measurements, 
buy a linear hall sensor you can find that covers the range of interest, 
and make your own - all you need is a power supply and some kind of 
indicator.

Modern hall sensors are well compensated and provide ratiometric output 
proportional to magnetic field strength.  Uncalibrated sensors cost a 
buck or two and individually-calibrated ones are $25 each,  still 
cheaper than any Bell probe you're likely to find.  Ref::  
http://www.allegromicro.com/en/Products/Part_Numbers/1321/

A basic intro to hall effect sensors and terminiology can be found at  
http://www.allegromicro.com/en/products/design/hall-effect-sensor-ic-applications-guide/

73, Bob W9RAN