I do not think that db2look can supply the password. This is because the password is maintained by the OS and is usually encrypted with an algorithm that is basically one way. This means that the password that is stored cannot be decrypted easily. Password checking is done by encrypting the inputted values and checking the result against what is stored.
Besides having the password in an uncrypted format in some script file is not a good idea anyway. It is a big security risk.