I am afraid in this way you are telling where the channel to write, not where to read from.
It finds that in the control file and I am afraid there is no way to change it
Maybe you can try the following
At the source, make a directory on the disk and backup the backuset to that directory ( I think that should work in 9i as well)
At the destination, make the same directory, copy the backup pieces there and restore from them ( of course you will need the control file from after the backup backupset)