Honeywell Hall Effect Switch

[Piero Andreini]

I recently bring back to life a Texas Instruments DS990 Model 1 but unluckily many keys are faulty.

It use the Honeywell Hall Effect Switches model 1A3S

http://deskthority.net/wiki/Honeywell_Hall_Effect

Somebody can help me to find them or any solution to replace them with other switches or other sensors?