Disclaimer: If you have an electronics store nearby you'll find everything cheaper simply because you can buy just the necessary quantities.
You'll need one Arduino micro, which costs on Amazon 9.99.
https://www.amazon.com/AITRIP-ATmega32U4-Compatible-Leonardo-ATmega328/dp/B08BJTS2N8/ref=mp_s_a_1_11?crid=1XA1Y64B0Z61&dchild=1&keywords=arduino+micro&qid=1635089618&refresh=1&sprefix=arduino+micro%2Caps%2C301&sr=8-11
You'll also need one linear hall effect sensor, which I found it costs 0.80 cents a unit, but in Amazon they usually sell 10 or more.
For the mechanical system I used shelf tracks I already owned, so I did not need to buy it. https://www.amazon.com/ClosetMaid-2800-ShelfTrack-12-Inch-Standard/dp/B00002N83Q/ref=mp_s_a_1_3?crid=236NCLFX3CNC3&dchild=1&keywords=shelf+track&qid=1635089897&sprefix=shelf+track%2Caps%2C428&sr=8-3
One or two magnets
Ball bearings if you wish https://www.amazon.com/Groove-Bearing-Bearings-Skateboard-Printer/dp/B07FGVFN6F/ref=mp_s_a_1_17?crid=34QIT66PBAAE9&dchild=1&keywords=8mm+ball+bearing&qid=1635090162&sprefix=8mm+ball%2Caps%2C364&sr=8-17
I used thick rubber bands for the centering force, but other people use springs. Both methods work. With rubber bands you have to change them occasionally but I bought a bag of 100 and I don't think I'll use 100 rubber bands in my entire life.
The layout is similar to this one (it isn't mine but very similar). It's also not pretty, but it gets the work done and I spent 20 bucks two years ago.
https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcTQZt38JUb70HOhbbm4PpIEFnLIHW8kHS6ZTg&usqp=CAU
For the software you'll need to use the famous joystick library for Arduino and configure it to read your magnet values read by the linear hall effect sensor. There's a ton of Arduino guides online. I used a mishmash of them to create my own, but this one is much more comprehensive (and expensive) than my own and he includes code.