Hi hi.mo
I recomend you to buy the sparkfun buttons from a distributor. I bought them searching at an electronic online shop. It cost me about 60 euro 4 4x4 button pads (64 in total), including transport.
About the leds, I recomend you to use ones that keep nice with your faceplate. If you use a black faceplate, i’ll recomend you to use blue/red Leds. If you use a white faceplate, orange leds, and successively.
Hope that it helps and sorry for my english!