I found one here for $30. http://www.sewingpartsonline.com/...
I buy my parts, etc from this site and so I did a quick check. They are very fast with shipping. And quite reasonable with their pricing.
I am glad you posted.
I think your link is the same as the one I posted but knowing the site is good to deal with -- helps us all. Thank you and a flower for you
Either a Viking repair shop or dealer might be able to help you.
The first link is for the part. I found one on Ebay in "new condition" but they wanted almost $50.
The second link is just a blog I found describing the machine and it has reference to age etc.
It seems your friend received a good machine.
The third link is to Viking for a download (not free) of the manual. A copy can be purchased elsewhere for $10-15 for a copy.
You are welcome. I hope you help her get it up and running very soon. Good luck!