Since I can't seem to find the grosgrain-trimmed cardigan (maybe one of the awesome WWEPW readers can help me out here - you guys always pull through when I need you!), let's take a look at Emma's enamel flower brooch.
In Episode 5, Emma wears a red-white-and-blue enamel brooch, and it's the star of her outfit. This blue flower is no different.
A quick search for "vintage flower enamel brooch" or "vintage enamel pin" or "enamel flower pin" on eBay or etsy will turn up dozens of great finds.
This site, Morning Glory Jewelry, has loads of fabulous vintage pins in stock to spruce up any plain cardigan. A few of my favorites there:
Aren't they fabulous? And they carry many more. I kind of want all of them.