What exactly do you mean by a "transistorized subtractor"? Are you looking for an analog subtractor circuit? Or a digital circuit? Either way, these can be somewhat complicated to design, especially the analog version. An op-amp can do an analog subtraction very easily. There are many websites that should have example circuits. Look up on google for "op-amp subtractor circuit" If you don't have much luck, try other search engines like Yahoo or lycos or dogpile and also try changing the search terms by things like leaving out the word circuit. But I think you'll easily find them on-line.
If you don't, you can contact me and I'll help you further.