I had a similar hard-to-find bulb from a track lighting fixture i purchased at Costco. It was a MR16 bulb, the base was 2 pins and looked like alot of the 12v models that use the same style pin base, but this one was 120 volts, 50watts. I ended up finding bulbs for this track from
Buy Lighting.com I considered their pricing reasonable and they arrived in about 4 days. Only used them once, but it was a pleasent experiance, and they actually had the bulbs which is more than i can say for any retailer around this area, including some electric shops selling many many fixtures.