Toshiba Satellite S75-B7314 bad keys in keyboard

Search eBay for Satellite S75-B7314 Keyboard and you should find one. Make sure it's the right layout (i.e. US/UK/etc).

I don't see a guide for that specific model but they're all pretty much the same. Take a look at 2 or 3 similar models. Sometimes there are 1 or 2 screws on the underneath of the laptop retaining the keyboard - if so they may well have a little picture of a keyboard by them. Then it's simply a case of releasing the keyboard by inserting a thin tool such as a Jimmy to release the catches, which may be along the top or along the bottom of the keyboard. It then lifts out, taking care not to strain the ribbon(s). You will then be able to see the precise layout of the ribbon(s) and compare it with the picture in an eBay listing.