You can do one of three things.
1. Install a PATA drive (IDE). Either a normal HD or a PATA SSD (expensive).
2. Buy an MSATA drive with an MSATA to IDE converter (it's the same size as a laptop drive.
3. Buy a SATA SSD with a IDE/SATA converter with an eye to the small space you have to work in.
#3 will probably be the hardest to pull off.
In any case, all PowerBook G4s have a PATA interface (IDE). Both Tiger and Leopard and above will show you the SATA column in System Profiler because Apple has no idea what system OS X will be installed on. An Intel Mac with a SATA drive, a PowerPC Mac with an IDE drive or a PowerPC G5 which also uses SATA. The columns do not go away simply based on the type of system OS X is installed on.