The Wilton Cake Decorating book has featured several and if you go to the back of any European decorators book they usually have templates but the template would need to be sized to fit your particular cake tier.
Not sure if this will help you as its a book preview from online. Theres a collar template on pg 287, its a full color, but you'll need to click on the page arrows at the top until you reach that numbered page.
I strongly suggest like the others, that you find a book on royal icing and runouts though. They'd be a lot more helpful for the measuring that needed, whereas links don't always provide that stuff.
http://books.google.ca/books?id=ld1Q0pkg6s8C&pg=PA224&lpg=PA224&dq=royal+icing+collar+templates&source=bl&ots=URhO24Hxjs&sig=JDWiYDZbKWfjkXKw0-_5n-GDiOo&hl=en&ei=GHqjTcfbK46ssAP51cT6DA&sa=X&oi=book_result&ct=result&resnum=3&sqi=2&ved=0CCcQ6AEwAg#v=onepage&q=royal%20icing%20collar%20templates&f=false
I've actually taken out a few books from the library that had collar templates in the back. I found one on Amazon that you might be able to refer to
http://books.google.com/books?id=Z2gy-JXou3wC&pg=PA172&dq=runout+collar&hl=en&ei=ioGjTYGXMorA0QHlx5SjBQ&sa=X&oi=book_result&ct=result&resnum=3&ved=0CDIQ6AEwAg#v=onepage&q=runout%20collar&f=false
HTH
There are several ways to do templates - you can buy a royal icing book - I would recommend Eddie Spence's book- He is the undisputed king of Royal Icing (and my tutor) or there are other books - an old one is called Confectionery Design by Lindsay John Bradshaw
photo copy the designs and scale them up to the size of the cake - remember that they will need to actually rest on the cake so the inside edge should be abvout half an inch smaller than the royal iced cake
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