acctually you can convert normal B&W negs into slides... but its a very troublesome process. requires two baths rather than the normal 1 bath, but its pointless, useless your gonna show your work on a slide projector.
B&W slide processing is only available in a few countries. Very specialized as it is hand done and also very costly. About S$30+ and above per roll. Countries where this is available to the best of my knowledge : Japan, Germany, UK. Duration would be from anything of a few days and more.