No POSIX "id" command, but have "gid" - how to use that?

[Skip Montanaro]

I've stumbled on an old problem:

byte-code: Couldn't find a POSIX `id' command

I am trying to fetch a file from a Solaris 10 system. The
only id commands are in /bin and /usr/bin (likely the same
executable). I do have a GNU "gid" command. Setting
tramp-remote-path won't help. is there a variable I can
set which either specifies the complete path to my gid
command or which allows me to say that "id" is actually
spelled "gid"? A quick check of the various tramp 

Thanks,

Skip Montanaro