Footrest with small footprint

Hi there, I'm looking for a footrest with a small footprint for under my desk sit/stand desk. I'm not sure of the model but it's a Flexispot, and it has a horizontal bar running between the two legs that is making it difficult to fit a footrest under there.

I have the amazon basics one that rocks back and forth and it's fine, but the mechanism underneath is too deep and it the horizontal bar. I would need something smaller altogether or with a smaller mechanism underneath, has anyone solved a similar problem? My feet are small so surface area isn't an issue.

Thank you!