Just go to any auto parts store (Napa) or even Walmart to buy a light. The links above are just repackaged truck lights that have been marked up.
You can find them for even cheaper on Ebay..any 2" to 2 1/2" LED round marker light will work.
I've been considering doing this exact setup bit kind of want to build it myself. I haven't been able to find the grommet mounted leds locally. At least not in anywhere close to the right size. Any ideas?