The ball and sensors in my mouse had become clogged and damaged, causing the pointer to skip - usually when I was trying to do something that demanded a precision click, like closing a window. Also, the cord was too short for the distance it was required to stretch, and often snagged or got yanked out. The constant minor irritation this created had lowered my tolerance threshold for other irritations, making me snap much more easily. (This very scenario is described in Zen and the Art of Motorcycle Maintenance, which I was sidetracked into picking up yet again last night, only with a dripping tap.)
After a brief online search, I found this. It might look as if it has a gigantic bubo sprouting from one side, but it's perfect for my needs. The only problem was that it's not featured in our official stationery catalogue, so I needed to explain to our stationery person why I had to have this particular beastie.
After letting me ramble for a few minutes about my vital web team work, she said: "Just tell me your wrist hurts, love."
So, offering a silent prayer for forgiveness (since I know several people who genuinely do have RSI and suffer agonies with it), I told her it did.
The mouse came this morning, along with one for my boss.
It's like Christmas in here.