The best solution I've found is RPM (Rust Prevention Magic) from ECS Automotive, although it requires a little work to apply since you have to heat the item with a heat gun before applying it. It will last a while though as it has passed a 1,000 hour salt spray test (automotive testing).

If you want to avoid the heating, Boeshield T9 is easy to apply, but in in auto application is only rated for 6 months.

These are both wax based products. Most other solutions are going to change the appearance of the part.

After de-rusting with evaporust, I usually either wax the part or spray it with gloss Polyurethane. Wax seems to keep the mirror shine, while poly dulls it a bit.

Considering that you are also dealing with a flaking surface and drastic difference in color, I might be tempted to spray with chrome spray paint to cover those spots to make them less obvious. However, you might want to test that on another part to see if the results are passable.

Some might argue to spray with poly first to lock-in the flaking, then spray with chrome paint to match the color. I'm not sure which approach might work better.

Looks like it need to be re plated to be 100%

Once your plating rusts and gets to the point that it is, there is nothing but replating to brink it back. For me, "Looks like chrome" paint never looked good enough. If that part is hidden, then maybe it will work for you, but if your like me and even though you can't see but know it's there, it will still bother you. ; )

is it cost-prohibitive to have the finish removed completely and then rechromed? you could sand-blast the whole thing and then electroplate a nickel finish - though I don't know what it would cost to get all the stuff for it.