That's wild that you mention the Portfolio because I was just yesterday trying to remember what John Conner was using to hack the ATM in Terminator 2.
I'm fairly sure it was one of those.
Apparently the Psion 3 was also released as the Acorn Pocketbook, and that's another very important British computer company. They actually became ARM which is used in basically every modern phone/tablet.
The wiki shows the Psion 3 had a travel-modem that would give it connectivity, but in 1991 I'm pretty sure most people's experience of the internet was just BBS, Usenet, and maybe email servers? People were probably playing all-text MUDs back then too I think.
What did you use your Palm devices for? Was it also like your phone?

Even though I was late to getting a cell phone; a bunch of my friends had T-Mobile Sidekick's also marketed as Danger Hiptops.
They were the first phone that was more like a computer, and what really caught my attention was they had AOL Instant Messenger which we all used back then on our computers.
They also had "real" web browsers that worked, and they were designed to be used in landscape rather than portrait.
The founder of Danger Inc. later created Android, and the Sidekick's also made heavy use of Java.