Here are a couple that seem to come up a lot in my searches. There are more expensive ones, but that's where if I'm going to spend a few hundred dollars, I'd rather just buy a whole desk!

https://www.amazon.com/3M-Keyboard-Platform-Comfort-AKT60LE/dp/B001B0DCOO/

https://www.amazon.com/dp/B01H7UGD7Y

I have a desk that I could install one of these long tracks on, but there are clip-on options for desks with crossbars or that otherwise couldn't take an installation