I can offer another suggestion: you can ask your bridesmaids to buy a dress of a certain color and material, and let them choose their own, individual dresses. One of the reasons it can be a bummer to spend money on a bridesmaid’s dress is that the dresses tend to look very bridesmaid-y and can’t be worn again. My matron of honor and maid of honor both wore light blue silk dresses. The lengths and styles of the dresses were different, but because they were the same color and material, they looked beautiful together. And it looks really nice in the photos, too—they match, but look like themselves at the same time.
Of course, you’d want to be specific about the shade of the color—light, medium, or dark.
Also, at the wedding rehearsal dinner, you’ll have an opportunity to thank your bridal party and give them each a gift. Some brides choose to give an accessory that they’d like the bridesmaids to wear—which enables you to request that they wear something you’ve chosen, without making them pay for it. For example, a pretty bracelet that can be a keepsake, or earrings, or perhaps a shawl to throw over their shoulders. Or you can give each of your friends a personalized gift.