Binary Encoder Circuit
What you need is called a decoder.  Although I don't believe there is a 7 to 128 decoder, there are 3 to 8 decoders (maybe even 4 to 16). If you use 3 to 8 decoders, you will need 16 of them. If you use 4 to 16 decoders, you will only need 8.  Follow the manufacturer's instructions on how to cascade them, and you will have your 7 to 128 decoder.