In 2015 a jeweler friend referred me to a fabricator who makes small-scale art and jewelry items. I had the fabricator make up some tailpieces out of stainless steel, bronze, hard nylon, and some other materials, and the results have been pretty good.
Presently I have copies of the S.S. Stewart Common Sense tailpiece with the rosette (in ivoroid; $60), without the rosette $40, with and without the lug that projects beneath the rosette. I also have copies of Fairbanks, Stewart, Bruno, Haines, & other sellers tailpieces in hard nylon (originals were ivoroid or ivory), most are $25 ea. I'm also working on tuner "buttons" modeled after vintage tuner pegs which will fit on modern geared tuners.... I should have these debugged & available by mid-March 2016.
I have been getting dimensions for vintage, proprietary hardware, such as the Cole Eclipse dowel yoke and dowel-end neck adjuster, Gatcomb's "Little Gem" neck adjuster, a zither banjo 6-string tailpiece, etc. as instruments come through my shop, and will have these parts made up if anyone needs them.
I can also reproduce small metal parts on-demand. Larger metal parts (such as large or complex tailpieces) are generally fairly expensive for me to reproduce. I also tried to have the fabricator make up some vintage shoes (eagle, shield w/ stars & bars, etc.), but these are also generally more expensive than I think that the market demand will support.
I have been posting more complete info on my Yellowstone Jewelry FB photo album: https://www.facebook.com/media/set/?set=a.786738851434879.107374184...
Send me an e-mail if you're interested.