I'm looking for a Hall sensor where the output goes HIGH with the application of a magnetic field and goes LOW when it's removed, (non-latching). Is there a unit available? All I see are the opposite; where the output is always high and goes low with the application of a magnetic field. To be used as a simple on-off switch.
Thanks

 

Various types of Hall sensor interfaces

https://docs.rs-online.com/54e9/0900766b80025c32.pdf

 

Many types of Sensors have an "Open-Collector" Output, almost exclusively.
Many also can't handle very much Current,
and therefore expect an Amplifier of some sort to be used as
an interface with other Components that may require more Current, or a Voltage-Level-Shift.

Usually this is completely accepted as a "given" when starting on a project.

If You are working with a Micro-Controller, it presents zero significance.
If You are working with an Op-Amp, it also presents zero significance.
So why, or how, is this presenting You with a problem ?
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Use a simple NPN transistor to invert the signal.

 

You can use non-latching Hall effect sensors that output HIGH when a magnetic field is present and LOW when it’s removed. A few good options would include the Honeywell SS441R that operates between the 4.5V and 24V range and also responds to the South pole of a magnet. Another choice is the Allegro A1101EUA-T, which functions within a 3.3V to 5.5V range (ideal for low power). The Melexis US5881 is also a suitable unipolar, non-latching sensor with a broader voltage range 3.5V to 24V. The Diodes Incorporated AH3372 is another option. It provides a digital output, turning HIGH in the presence of a magnetic field, and works with voltages from 3.5V to 20V. These sensors are effective for simple magnetic on-off switching and are available in both surface-mount and through-hole packages for easy PCB integration. Another option to consider is the Infineon TLE4905L, which offers a similar non-latching behavior and operates within a voltage range of 3.8V to 24V, providing flexibility for various applications. All these sensors are designed to respond to the South pole of a magnet (as per your application).

 

As @nsaspook mentions, there are sink or source versions available, you need Source version.