Try ebay! NO lie, you can find anything here. Try searching, "vintage chandelier crystals." see what you find! I always select "lowest price first." that way I can build up the price as I look from page to page.
Depending on where you live they may or may not be easy to find. Start by checking out any store that has bead making equipment and supplies. Some art supply stores sell lapidary supplies, and they may prove to be a good source of crystals. Look in local craft shops and attend any gem shows in your area. There are also a lot of online sources for crystals, which you can find by doing a search on crystals, lapidary or gemstones. Happy hunting!