Here are some shells from vintage stock (about 1940's). They all measure 1/4" and under. The orchid ones are the largest of them. They are available in various quantities and prices.
From top left:
Tan-earth tone - 50+ - $1.85
Mixed blue - (You might find a couple of imperfect ones, but I have added extras.) 70+ - $1.95
Orchid - 40+ - $2.25
Mixed colors -some metallic - 60+ - $1.65
Mixed purples - 40+ - $1.85