Is there some way or some part from any manufacturer that you can use to attach disc brakes to the rear end of an old bike that doesn't have the (not sure about the word here) flaps at the back where they're usually attached to? I don't know the word for the part that's missing from my friends bike so it's kind of hard to search from the web and from this forum as well I've asked from all my local shops (Finnish) but none seems to know.

Any help here would be appreciated, we've been trying to figure this one out for a long while now.

Ps.. my friends bike is Marin palisades trail