oh man, my space is not exactly presentable, but it's basically one of these
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with one of these mounted on each side to a custom desk/shelf, though any end table that's approximately the same height as your chair arm would be basically the same.
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keyboard in lap and trackball on the little swivel table or chair arm/side desk. If were a mouse-man, the side table would need to be the same height as the chair arm of course. It is anyway since I built it, but it doesn't have to be for my use. it makes it handy to have it be basically an extension of the chair arm though.