It turns out it does exist after all, although not in the otherwise excellent Applied Engineering Repository. You can find it on ftp.asimov.net here:
You run a script on this disk to install the RAM driver and utilities to your Pascal boot disk. The next time you boot, it creates the RAM drive and copies all Pascal system files it can find on volumes #4 and #5 to the RAM disk, then makes the RAM disk the boot disk (required for UCSD). It's smart enough not to nuke the RAM disk if there's already a valid Pascal volume on it, so you can reboot your system without losing data.
Makes a huge performance difference if you actually play with the P System.