On my last car, auto dim mirrors with lights were a $400 option. So I went on Ebay and got a used one for cheap and installed it.
No reason you can't do this with an FJ. Might be a bear getting it to fit the ball mount but where there's a will there's a way.
Absolutely stupid that they put such poor lighting in this truck. Not even any floor lighting and even a goddam $10K KIA has that.
eBay Motors: 96-00 Sebring Convertible rear view mirror auto dim map (item 400010174732 end time Nov-24-08 20:46:03 PST)