No one suggested it yet so I will... First, I wear reading glasses and my wife can't read anything at all without reading glasses.
Consider getting a Perdix AI dive computer. Its huge and bright and should allow you to read it underwater.
There is often more to see that is up close and small than just one's computer.
I can read my Shearwaters just fine without reader lenses. But, what about reading the LCD display on my camera? Or having a nice look at a nudibranch from up close.
I currently own 5 Shearwater computers. But, they are not for everyone and I do not believe they are the answer to "my computer is too small and I can't read it."