LM107 OpAmp & LM338 Voltage Regulator

[TinselKoala]

Dave, did you take a look at the link I posted earlier? The circuit there is cheap, small, reliable, and you can also use it to control DC motor speed. (It's a basic PWM power supply).
If you don't get the fancy box and knob, the parts will cost you under 10 dollars, so you can make one for each lamp and still spend less than the cost of that transformer.
The diagram is about halfway down, and there's clear explanations of how and why it works.

http://www.ctshooter.com/dimmer.html

[derricka]

Hi Dave,
I have looked over Tinsel Koala's dimmer circuit, and it appears to be a great choice to go with the power supply I recommended earlier.
The MOSFET will need to be upgraded if you want to dim two 50 watt bulbs together, so let me know if you intend to do this.

If you really didn't want to spend any time soldering parts together, you could consider the lighting4art.com C150 magnetic transformer rated at 150 watts. This one is a bit bigger, heavier and more expensive ($108.19), than the power supply I suggested, but will work with industry standard 120 volt dimmers. I should warn you that 120 volt dimmers usually flicker at low brightness levels.  The circuit suggested by TK should do a better job, as it operates at a higher frequency, but if you want to use TK's circuit, use the electronic supply I suggested before.