I never bothered with a case for my IIIc and it's over 4 years old. The flip cover for the IIIc protect the LCD as does the T|X flip cover.
However some drop their PDAs so for them more is needed.
From memory, you can use any case that fits the T5
I am currently looking for a case for my Palm TX. I was thinking about getting a hard case with cutouts for easy access to the stylus and all other functions on the top and bottom of my PDA. I was wondering if anyone had any input as to whether this is a smart decision, as I have noticed most third party cases run around 25 dollars, rather than the 40 or so Palm charges. Also, is the hard case the way to go, or should I invest in a leather case? I'm just looking for input on the cheaper cases (i.e. great deal or waste of money.) This is my first PDA so I wanted some input before I invest even more money into this thing. Thanks in advance.