I located an '86 or '87 Reliant sedan in a "private" yard about a month and a half ago and I bought the rear taillights for my '85, I'm heading back either later this week (Hopefully Saturday) or early next week for a few more bits from an '81 Aries that's there. Its an LE so there should be a passenger mirror. If the mirror is there and in good shape I'll snag it for ya. This guy is easy to deal with so it won't be a fortune, You will obviously have to cover the shipping to get it to you and I won't know that until I package it etc. If this is good for you let me know. I also came across an '85 Aries in another yard but I can't remember if it had a mirror or not but that's another yard I'm going to revisit soon I hope I convinced that guy to hold onto his group of K's for a while as he wants to "clean up" the yard
If either of these options does not work out I have also located a Dodge 600 Turbo and I think its the same mirror but its chrome would that be OK (thats in a third yard I've visited but its close by) . I go there often as he has Fifth avenue stuff so I pick at that....let me know