Give Rick or Selida a call with Bathtubs and Fixtures. Their number is 422-9499 or 422-3506 and they have a website, bathtubsandfixtures.com. They do most types of tub repairs and refinishes. They have done several jobs for me, all with good results.
I just had a cast iron tub refinished and a couple of chips repaired for $650. It's a several step process they use, starting with an acid etch. When it's finished, it looks like a newly glazed tub, not the painted style refinish.