Over the years we've used a couple different products for rally wheels. Valspar had one that was a pretty good match, but in their infinite wisdom they decided a couple years back not to deal with 'job shop' powder coaters directly and sell through a 3rd party. Service level went down, prices went up and availability is inconsistent at best. So chances are you may have a hard time finding someone in your area who still can access the Valspar stock colors.
Tiger Drylac has some good silvers that are close, and they're easier to deal with by far than Valspar, plus the powder can be purchased in 5 pd packs, so if the coater doesn't carry the one you pick out, it can be obtained without breaking the budget. Ask to look at the color cards. Word of caution, look at them outdoors in sunlight. Interior lighting can play games with color perception, particularly silvers.
Axalta is another option (formerly DuPont) for you. Priced well and perform well. Again, look at their stock color card.
I believe TCI had a pretty good match as well, but they're something of a bit player in some parts of the country.
Another thought: try and avoid the silvers that require a clear top coat for outdoor use. You pay for painting the rims twice and I've not been happy with the clear top coats for this application. Stay with a single coat product. They tend to be what's called a TGIC polyester product. Europe is down on TGIC's so some mfr's have tweaked their formulas to be TGIC free.
Having said that, I'm sure you can find someone who insists clear coat is the only way to go. I'm just passing on what I've learned running a shop since 97.
The coater then needs to be careful about thickness consistency and gun settings, to keep the color looking the same throughout the rim. Some will darken a bit when put on heavy. If the painter uses the wrong tip, the metallic content may not lay out well enough, just like with liquid metallic.
Hope this helps.
