I just phoned my local KTM place in Kendal (Cumbria, UK) and the 2017 mirror (complete as far as he could tell) costs £93.54 each side, including VAT, which works out as $117 each (using Google for a rate) plus shipping. I'm guessing there is a better way
The most econmical way to go about it is to buy the current version US mirrors which are the same here in the states, then get the EU signals to put in them from some one that sells from the EU. Other members and myself have used KFM. They are great to deal with and you can set up an account easily, plus they have an ebay store so they may be able to place the parts on it.
When it comes to wiring them up I just tapped into the loom that goes to the combo insturment, that is how the EU version connectors are setup. Note there are two green wires in the loom so you need to check to make sure you have the correct one.
I talked to my local dealer, and he said there were no part numbers for the 2017 RC390, and pointed me towards fowlers in the UK to order, but they only have until 2016 listed, and that's for an RC250.
But I know the mirrors got redesigned in 2017, not sure why no one can order the parts though?
2016 part numbers, anyone confirm they're different than 2017?
93812041033
93812040033
Sorry, gave the EU part numbers. link below will get you to the 2016 parts fiche, or you could search threads on forum where it has been posted before.
They look exact same as 2017 shown on KTM web site BTW.
FWIW,
I think they probably are referring to the original 15 to mid / early 16 small mirrors(again search, members on the forum have 16's with both variants), the mirrors in the article from your link and the KTM page are the same ones that I have on my bike now. I could post more pictures for comparison but it would probably be best to wait and get a set of 17 mirrors to be sure and then measure them and let us know the dimensions.
I got the mirror risers, so I'm trying to get the best rear view I can, which is why I was hoping the 17 would be even better than the 16. Just let me know where to order and I'll pull out my digital calipers when they arrive.