I just got a sweater guard off of Etsy, but I think it's the only one the seller had, so I can't make any kind of recommendation. I did a search for vintage sweater guard and came up with about 200 results, so I just picked the one that struck my fancy the most.
As for brooches, my favorites are from TillyBloom on Etsy. Everything is based on Victorian illustrations, which I think are great, but I think it's probably a love it or hate it thing.
I have this one, called the Automated Daydreamer.
And I am totally lusting after her At The Library Brooch