Maybe you answered this before, but I missed it. Why not use a latching bi-stable relay. There is a choice of single- coil of two-coil, depending on how you want it to switch. I was surprised the DigiKey price for the Schrack is only $2.50.
http://relays.tycoelectronics.com/schrack/pdf/RT1bistable_d.pdf
John
http://relays.tycoelectronics.com/schrack/pdf/RT1bistable_d.pdf
John