Most people who want to try working standing up do not want a project. They want to stand for part of the afternoon without replacing a desk that is otherwise fine, and without a motor, a controller and four hours of assembly.
There are three honest routes. They are not equivalent, and the trade-offs are worth knowing before you spend anything.
Route 1: a second, mobile surface
Keep your desk. Add a small height-adjustable table on casters that rolls in when you want to stand and rolls away when you do not.
The Lyft Mobile Sit-Stand Desk at $95 and the Rulle Height-Adjustable Side Desk at $129 both do this. You adjust the height manually, which takes a few seconds.
Trade-off: the surface is small — laptop-sized, not dual-monitor sized. It works well if your standing work is writing, reading and calls, and poorly if your standing work needs your whole setup.
Bonus: it is the only route that is also useful when you are not standing. A rolling side table ends up holding a laptop next to the sofa more often than it ends up being a standing desk, and that is a feature.
Route 2: raise the screen, stand on purpose
The cheapest version: put the monitor permanently at standing height on a tall riser, and use a stool or a high chair for the sitting part, rather than the other way round.
This is less of a compromise than it sounds, but it is a real commitment — the desk is now a standing desk that you sometimes perch at. Worth considering only if you already know you like standing.
Route 3: buy the sit-stand desk
If you have decided this is how you work, a dedicated sit-stand desk is better than any workaround. We do not currently sell a full-size powered sit-stand desk — the Lyft is a compact manual one — and we would rather say so than talk you into the wrong product.
One thing to sort out first
Whichever route you take, deal with the cables before you move anything up and down. A cable run sized for a fixed desk will snag the first time the surface changes height, and a snagged cable is how a monitor comes off a desk.
A flexible Rygg Cable Spine is built for exactly this: it bends through the range of movement instead of pulling tight at the top of it.
A realistic expectation
Most people who switch do not stand all day, and the ones who try usually stop. Standing for part of the day, and changing position more often, is the easier habit to keep — so buy for the version of this you will still be doing in a month.