I never tried it, but if you're using Wall Market, then there might not be... at least, not that anyone knows of.
If you want to get rid of Slots and changing limits doesn't do the trick, then maybe (and this may be a little complex) you could do the trick by changing around character IDs? It seems to me that with Cait Sith's character ID, he always uses Slots at level 2. Most likely, you'll get a similar problem with Tifa. Any other character should not give you trouble therefore.