Actually it doesn't matter much which brand stop and fix you will use: they are all ok as long you use them as intended. They don't influence the print quality. Stop can be replaced by diluted table vinegar (a dilution of about 1+ 4 should be about right) and some people even prefer a water rinse. Any general fix will do aswell. Keep track of the capacity and seperate the working solutions for prints and films and you're settled. I would get something odorless that is readely available and not to expsensive.