Measure the hole for the switch, and search for a snap-in switch of the right type that fits the hole. There's a fairly good chance it's standardized. Ideally you want a switch that's rated for DC use. (The last line embossed on the old switch says that it's rated for 3A at 14 V DC; the solid line with the dotted line means DC, while a squiggly line means AC.)
There's no need to find precisely the same model number of switch so long as the physical dimensions and electrical ratings are acceptable. I suppose finding one that's whitish would be preferable aesthetically speaking.
Places like Digi-key and Mouser, among others, sell very many different brands and styles of switches.