I had exactly this same need, and did -not- want to use outlets or an entire system for just two switches at a place I will probably not be in another year or two. I found what I was looking for at a local HW store recently turned A*E. The brand is "Heath Zenith", the model is BL-6133-WH (the last two letters are the color, in this case White) I believe.
The design is: you replace the original wall switch with a switch that also has an antenna that talks to the "wireless" switch (mounted wherever you want) and the replacement wired wall switch also has a master kill switch on it that will disable the action of both the wired and wireless switches. They are identical from what I can see to a "Chamberlain" branded product that is no longer available on amazon, so I won't bother linking.
Unfortunately, they are quite cheap. Of the two switches, I ended up with two different problems, one is a channel D, and one a channel E. I have not attempted to swap around parts to see what's up… interference could of course be a problem as sometimes the one will not do anything for 19 out of 20 flicks, however it actually seems to be related to poor mechanical design on them both: you can complete the circuit by just tipping the switch about a quarter inch or so, at which point it will just slide back to its original position, unless you keep going to push it over. This of course could be how they are used if one was so inclined, but I like the idea of being able to look at a switch and know what's going on with it (as I'm sure we all do!). The inconsistent one also needs force to be applied toward the wall to work consistently I've figured out… it's exactly what we were both looking for (you and I) but a bit on the cheap side...
I paid around 30$ each out here in California, and I haven't thought about acting on the 1 year warranty until now… but it seems a design flaw, as, if I remember, the replacement wired switch has the exact same behavior of completing at a quarter inch… yuck! sigh… truthfully, I'm not sure I would get them again… but then thinking about putting my hand in a crack to turn the switches with somebody in my arms and I guess it's better, even though disappointing in some ways.
Check the manual at:
http://www.heath-zenith.com//data/manuals/205259-01A.pdf for some pictures and install plan.