Dr. Ross,
I like the external drawstring idea. Seems like I've seen it somewhere before.
Would it make life easier if you set up the order page similar to:
Step 1. Pick the bonnet color.
Step 2. Pick the band color.
Step 3. Pick the optional cockade color.

and have samples of the colors you're offering?

I must say, I'm not a fan of the cockade. I'd say leave that to Mackie, and let your bonnets be their own thing.

I hope you sell a truckload of them.