The little birds on the new Mui Mui pattern are so cute! Not sure how much wear you would get out of a detachable collar but White Lightning has done a great DIY here just like the ones sold by Mui Mui in case you want to. Unless you are a great painter, which I am not, I would probably do a plastic stencil of the swallow and paint/spraypaint my collar. White swallows on blue collar would be nice too.
Image source: The Chic Muse