Just bought one for a friend from my Janome dealer cost $5 Aus
I can highly recommend GoneSewingCompany on Ebay. If you go to his store, click on any item to find the "contact seller" button and email him with the your machine's model number and he will do his best to get you what you need, his name is David.
2nd link should take you to the search I did, of his store, for Janome for you.
The closest Janome dealer is over 75 miles away - in Eau Claire, WI.
I am a big ebay user so I did look there and I found one, but I was too upset to buy it as they wanted $8.99 and $6.90 to ship a small piece of plastic that probably costs only $1.00 to ship!
Thanks for suggesting it though as some people don't think of looking there.