I have a very similar mid century executive desk. I ordered these and haven't regretted it for a moment.

https://www.amazon.com/gp/aw/d/B01393H19M/ref=mp_s_a_1_41?ie=UTF8&qid=1469493273&sr=8-41&pi=AC_SX236_SY340_QL65&keywords=furniture+legs