Electronic toggle switch
If it's a "reed switch" you're talking about, they do indeed exist in SPDT form, though they're not as common as SPST N.O.. Also in SPST N.C. (normally closed) form. For example: 



If you want to reverse the action of a SPST N.O. switch, you may be able to do something like this: 

In the case of the BJT, make Rx about 10-20 times RL. In the case of the MOSFET, make Rx a few K ohms.  







simulate this circuit &ndash; Schematic created using CircuitLab