The best place to shop for these glasses is flea markets, antique shops, and estate sales. While usually finding an entire set is impossible or outrageously expensive, you can have fun picking one or two of your favorite patterns out to mix in with other finds.
Mixing crystal, pink glass, silver rimmed, etched, long stemmed, and goblets is great. In my opinion, the less matched the better.
Anthropologie always has a great selection at their stores and I found a few other vendors with some options to get you started.
1. Horta champagne glass, small from Anthropologie $12
2. Set of 12 Vintage Cut Crystal glasses on Ebay bid at $75
3. Vintage pink floral glass tumblers by 1GlassyDealer on Etsy $50 for 2
4. Rippled coupe champagne glass from Anthropologie $14
5. Helianthus Goblet from Anthropologie $8
6. Kate Spade New York "Gardner Street" Stemware at Bloomingdale's $40-$45
7. Vintage etched glass goblet set by OldNewsCollective on Etsy $10