Yeah, it's not extremely stable. Great for a laptop, not for a cup of tea.

Maybe look into small table like things that are meant for "dinner on the couch" type of situations, but height adjustable? Or something targeted at Camping - that's often lightweight and adjustable but relatively stable (and hopefully affordable).

https://www.amazon.com/RedSwing-Folding-Adjustable-Lightweight-Aluminum/dp/B07W4721C3/

https://www.amazon.com/PORTAL-Outdoor-Portable-Adjustable-Aluminum/dp/B07R3TFG3R/

https://www.amazon.com/HUANUO-HNTT-B-Comfortable-Folding-Adjustments/dp/B07DRGZMHQ/