Your best option is probably going to be a painted finish. The correct approach is to tell the ID/Client you can paint them (or know a painter that can paint them) and that you can provide a sample for (insert cost here).
The cost of the sample grill might be $200-300... whatever you think it might be to cover your time messing with it. Once you do the sample you provide it to the ID/client for approval. If they like it you'll know what's involved and can give them a price to complete the rest. If they don't like it, you keep trying (and billing) until you come up with something they do like or until they give up and ask you to just paint them to match the ceiling.
I had a similar request several years ago to paint speakers metallic gold to match light trims. I found a metallic gold paint and it actually looked good and matches the wood ceiling well. The metallic paint was tricky to spray, but after a little practice and getting my spray gun dialed in it went well.
This is the paint I used... I think they also had a metallic silver which might work for you. You might try experimenting with a scotch brite pad, fine steel wool or even brushing across the paint when it's still wet to mimic brushed stainless steel.
The paint apparently has real metal particles in it:
[Link: modernmasters.com]