Found several multisig wallet source codes but I can't deploy them in ethereum wallet because they can't be compiled. Either they use an old version of solidity or I get the error "No visibility specified."
You can give this a try https://github.com/ConsenSys/MultiSigWallet Thanks
I like this one:
Im working developing one of them. To be honest its better to try to use one of the zeppelin or gnosis instead of create your own because its more risky if anything goes wrong.