Ergotron WorkFit-S, Single HD, height-adjustable workstation with work surface. Easily attaches to desk. Monitor stand, keyboard tray, and additional work surface can then be lowered or raised to your liking, to accommodate both standing and sitting ergometric work setups.
For more info, see, for example: https://ergobuyer.com/workfit-s-single-hd-workstation-with-worksurface/