Deskcycle is the brand name. If these links doesn't work, just search Amazon for Desk bike. I'm sure there's others using the same technology and may be cheaper. Just something I had picked up.

DeskCycle Under Desk Bike Pedal Exerciser - Portable Foot Exercise Cycle for Sitting with LCD Display - Mini Stationary Peddler for Adults & Seniors, Physical Therapy Workout Equipment https://www.amazon.com/dp/B00B1VDNQA/ref=cm_sw_r_apan_glt_fabc_VF839TBM9N8C5FRVRQW7

Deal of the day: DeskCycle 2 Under Desk Bike Pedal Exerciser with Adjustable Leg - Mini Exercise Bike Desk Cycle, Leg Exerciser for Physical Therapy & Desk Exercise https://www.amazon.com/dp/B07BDRFMZK/ref=cm_sw_r_apan_glt_fabc_dl_2N8E9Q4RC372RNFMNQ51

I don't have that model, but do have the Desk Cycle. I keep it under my desk at work and try to use it a few times a week. It is completely silent and except for my knees bobbing up and down, no one would realize I am using it. You can set the resistance and get a pretty good workout on it. It is on the pricier side but I enjoy using it and it helps me concentrate.