If your desk is heavy, you can use a clamp on style. You have a couple different options:

Gator Frameworks - 89.99

VIVO- 49.49 - These do not have EVA on the clamps so vibrations will be worse than other models with EVA or fabric to limit vibrations.

Vondynote - 56.99

When it comes to Amazon, I would not purchase any other clamp on mounts besides the 3 listings above. GF should be the best quality - probably not worth an additional 40+ bucks but I would get those if you are not worried about the money.