Hey guys I just found this 40mm fan screen for us who run in grass and thought I'd share it, its perfect and dirt cheap.
https://www.newark.com/sepa/fm40/emc-fan-screen-grid-40mm-ss/dp/55Y9816
https://www.newark.com/sepa/fm40/emc-fan-screen-grid-40mm-ss/dp/55Y9816