Cubii and DesckCycle are probably the two leading brands when it comes to under-desk exercise solutions, and the (Opens in a new window)(opens in a new tab) is one of the former's best ellipticals.

Source: https://mashable.com/uk/roundup/best-under-desk-cycles-and-ellipticals-uk

If your budget allows, you may consider investing in more advanced exercise equipment such as ellipticals or weight benches to diversify your home workout routine.

Source: https://ph-microscope.com/how-to-stay-fit-at-home-5-easy-techniques/