Interesting timing; I came across my Series 3a in a drawer a few days ago and fired it up for nostalgia's sake! Worked perfectly, and I still love the way it folds away after use, but it also reminded me how far handhelds have come in the intervening 13 years or so.
By the sound of your post though, it did all you need, so why not get it repaired? You don't mention the model but typing "Psion repair" in to Google brought up a fair few possible hits. I recall a common failure point on some Psions is the ribbon cable; these can still be obtained and replaced. In a similar vein, I got my old iPAQ PDA repaired last year (I still use it for satnav) and the cost (to diagnose what turned out to be a charging fault and replace the motherboard with a second hand one) was peanuts. Thirty notes or so, I recall, including postage.