We had been planning to re-plate the existing door hardware, but it actually turned out to cost about the same, even a bit less for some doors, to simply replace the pieces. Sharon looked diligently for a good deal on the plating (she wrote at least half a dozen re-platers for email quotes), but the least expensive deal she was able to find was $14 per knob and $12 per plate which would come to $52 per door!
So, ultimately, when we found Crown City Hardware, we simply decided to replace the hardware on the doors. Their interior set is $49.99 per door and we believe it is solid brass—not plated.
We still haven't installed the screws on the new set because the locks came with phillips screws. We're going to buy slotted screws which are more accurate for the period. It is nice that these new sets can be installed and tightened up and stay in place without the screws.
They also sold a neat dummy spindle in order to assemble matching dummy knobs for our pantry doors.