I found a "new old stock" Philips amBX Extension Kit (SGC6101BD) on eBay for £1. This is the two fans and vibrating wrist rest which are intended to be added on to the basic amBX kit (speakers with lights). This dates to 2006.
This kit is useless on its own because it's designed to plug into the amBX controller, which was sold separately. But that's ok because I can make a custom controller.
I envisage a box that the two fans and wrist rumbler can connect to, which also connects to my PC via USB. Then I can have some software on my PC to control the fan speed and trigger the wrist rumbler for notifications.
I will experiment with also using the fans for quiet notifications that won't disturb my coworkers. Perhaps it will also be possible to create a compelling natural wind effect?
It's a good idea to Google the subject before starting work so I don't waste time or risk breaking things.
I found this Hackaday post which led to a blog by "Electrosthetics" who has helpfully published lots of interesting historical information about amBX.
The most important pages for this project are here and here, where they provide pin-outs for the fan and wrist rumbler sockets on the original amBX controller. The connectors on my hardware are mirrored from the drawings in the blog post, so I'm sure the blog post is showing the receptacles. My custom controller will need to match these pin-outs.
I'm surprised to see that the wrist rumbler needs 15V. Hopefully it will be acceptable at 12V, because I was planning on only having one 12V power brick supplying power to my custom controller.
Fortunately the connectors aren't custom so I don't need to re-terminate the cables. I can just buy suitable receptacles.
The fan connector is a 5 pin Mini-DIN. (The fans are identical - there isn't a specific left and right unit.)