Ergotron standing desk converter, something like this one: https://www.ergotron.com/en-us/products/product-details/33-341#?color=black although not sure if that's the exact model or not.  I haven't used it in years, and when I tried to I couldn't figure out how to get it to move up and down.  Maybe you'll have better luck!  If not, maybe it's at a decent height and can just stay there.  Also not 100% certain I have all the screws to attach the monitor arm but if not hopefully that's not too hard to deal with.  Pick up in Newton corner near Watertown.