Rina,
You can buy these from Digikey, Mouser or any supplier you normally buy from. You are looking for a metal film or carbon film 120 ohm, 1/4 watt resistor. Digikey
120QTR-ND are 10 cents a piece. You may even find them at Radio Shack. The hard part is meeting minimum order. I like Digikey because they have always been a reliable company and they support First in Minnesota.