Could you explain what you really want and what you will use it for?
gpg -ca will convert the input (wallet.dat) into a conventional symmetrically encrypted ascii text block such as this:
-----BEGIN PGP MESSAGE-----
jA0EAwMCZGu2org4FqJgyVXAHqwktVpZRZhDmGTlVnscUL6bxvPjyjv6cNXzKoCy
DBcr5tH3mBTDnvwSedBdJEI586w8PuahfdbRoritDrMqgT1KAsGMusMcERQh1gpV
V6dpo+ky
=oJ2k
-----END PGP MESSAGE-----
gpg with no flag arguments will decrypt it again. In both cases you'll need to provide a symmetric key, any passphrase will do.