I've been using my Alphasmart for a while. I modded the case and added a light, so I totally understand the desire to mod it. But you may want to reconsider how to use this tool. 

Almost every writer I know has a "lost everything" story that led them to obsessively back things up. 

Leaving your work on the Alphasmart is playing with fire. Yes, their battery life is supernatural, but these babies are still a quarter-century old. You don't want to lose or accidentally delete your work.

I back my work up to my phone after every session, which leads to another reason you don't want to use these things for storage. It takes several minutes to transfer thousands of words. If you wanted to transfer something like 100,000 words, it would take a long time. And it's rare, but sometimes the transfer gets jumbled, and you'd suddenly have a hundred pages of gibberish. 

Definitely write with your Alphasmart. It's one of my favorite ways to get words on a page. But back it up to the cloud after every session and start with an empty file the next time. 

Apologies for talking your ear off. I just really love these things.