A good place to buy Christmas bulbs in bulk (maybe pull them from a string?) is on eBay or through a wholesale site. Sam's Club, or visit Bronners.com (biggest christmas store in the U.S.) I hope you can do this so your Christmas tree is as pretty as you want it and I hope you have a very Merry Christmas!!
P.S. Check the base of the bulbs - you'll have to see if it's a common base to be able replace the bulbs with spares, or if you need to pull the bulb itself. In that case, once you pull it, you'll see 2 wires that hang down. Just grab a new bulb without a base, push the 2 wires through the holes, and wrap them around their corresponding sides.
Hope this helps!Can I change ALL the lights on my prelit tree?See if you can take it back and exchange it for one with clear lights - far easier and cheaper. :-)