I recently bought 2 LED remote controllers from Ebay for less than $10:
The controller allows dimming and blinking at different speeds in addition to dimming on and off:
Voltage is limited to 5 to 24 volts. The LED's may need current limiting resistors in some cases, but it can handle currents
up to 12 amps for Christmas lights. The remotes are frequency matched to the controller and require a CR2025 battery.
I used some male and female 12 volt screw on connectors to test them on an existing temporary LED
sink light I made using 12 10mm LED's that normally is controlled by a touch switch under the sink cabinets.
Since each 10mm bright LED uses 3 volts, I made rows of 4 in series and ran 3 rows in parallel. I just taped it all up!