As stated above, I recently purchased a very nicely made cloth over wood constructed viola case (Alfons Marcandella of Switzerland) with several problems.  One of two 6 mm by 26 inch long metal zippers (Riri) had a torn away tooth section from someone attempting to open the case with the zipper only partially retracted (the clasp was not near enough toward the hinge).  The other zipper had crooked teeth in the same area from the same cause.  The four bow frog keepers were very loose, and the bow neck leather string was partially missing.  The leather edge piping was coming loose in areas.

I looked into replacing the zippers and eBay and Amazon did not find useful matches.  I did find that YKK (a main manufacturer of zippes) had a new line of EYL luggage zippers that looked interesting.  Ultimately, my seamstress could not obtain them from her supplier and used standard 5 mm by 26 inch long YKK metal zippers.

The cloth was held on the wood frame by a number of screwed fasteners (about 30 in all) and I used photos to remembered where each went.  The bumpers only secured to the cloth.  I gave the cloth to the seamstress, she ordered the required zippers, and returned the cloth to me the next day (UPS is a wonderful thing).  Each zipper was $30 including labor and she charged me $10 to resew all of the leather piping.  

I used a piece of 3 mm diameter kevlar braided cord (900 lb breaking strength) to replace the broken bow neck string (shelf stock so I did not include a cost) and installed small o-rings on the bow frog keepers to have some resistance to movement (also shelf stock).  

I don't know how the seamstress did it, but the cloth fit on the wood frame perfectly and I used all of the same holes to secure the fasteners.

My original cost for the case was $20.  The cost to the seamstress was $70.  My labor and incidentials had a trivial cost.  

An interesting note.   The fabric color had features of both red and brown.  The seamstress insisted that she use a brown zipper, since that was the easy match.  She said that red zippers would all be too bright to blend with a classic material used on the case.  She was certainly correct, and the brown zipper looks original.