How to reject the 3rd spur of upconversion mixer

Two different frequency clocks are mixed to a new clock.

The IF (low frequency clock) signal can be degenerated to improve linearity.

But the LO (high frequency clock) signal is very nonliear. It has 3rd and 5rd harmonic, which are mixed with the IF signal.

Except the LC loading, RC filter, is there any other solution to reduce the 3rd and 5rd harmonic upconversion?

Thanks