Netscreen 100

Does anyone know where I can find a more recent rev of ScreenOS for the
discontinued Netscreen 100 and Netscreen 10 firewalls? I have a lab
project I'd like to use them for but the version 2.x of ScreenOS they're
currently running do not have the feature set I'm hoping to experiment
with. Since I can't even buy a license for these devices any more, does
anyone know where I can buy a disc with version 4 or 5 ScreenOS for them?

Much thanks,
Gary