I have a bottle of rack repair touch-up and it came with a bunch of tips as well. It cost $18 and change and was really tough to find. I can't use the tips on my Thermador because the tines are all looped at the top. One thing I did notice is that if you have the aqua blue colored tines, the blue touch-up is very blue and doesn't match very well. Fortunately, the bit of rust on mine is on the bottom of the racks where you don't see the touch-up.
My local ACE Hardware had white rack repair in stock, but would have to order the gray. You can try ACE if you don't have the blue coated racks and it will probably be cheaper, but you'll be on your own if you need tips to match.