It doesn't sound like a very good shop, they shouldn't turn you away because you want to do something unique. Find a new shop.
You can buy some of those parts painted on eBay, so you may consider looking there, also if you have an air compressor, and a paint gun you could just spray the parts yourself. It is not like painting a whole car, so you could just do it in your garage.
Also, I am not sure on the armrests, you may have to remove the fabric from them first to be able to paint them. But they won't be very comfortable.
I look forward to seeing pictures when you are done!
