Yes, it's worth looking for jewellers with an interest in 3D printing. There is a huge amount of jewellery on Shapeways already. I did ask on the Shapeways forums some time ago, but responses were all from people who were quite far away, and the only one in the UK who responded engaged in almost immediate mission creep (he wanted to build a 3D scanner to scan my hand so he could make a complete hinged exoskeleton glove, which is great, but it's going to take several years).

I don't know how important the springiness is, but the Shapeways solid silver is done using the lost wax technique. That's starting to get expensive but if fitting is the cost of printing a plastic splint, rather than £££ worth of private consultation, it starts being worthwhile, especially for replacement splints once the fitting is done. The stainless steel stuff I have from Shapeways feels pretty strong but it is decorative rather than functional so who knows? The important thing would be that the steel splints don't snap, which could cause injury; I suspect it's impossible to completely avoid this risk, but it would be bad if printed splints started snapping with everyday use.

However, this is what testing is for.