Fine mesh strainer (2 pack) to stop ingress of beasties. 
Get it on eBay and save yourself some pennies. Split the strainer in two halves using pliers and the two pack is now 4 strainers for pee spout.
https://www.ebay.co.uk/itm/266041056884?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=ZZJbcknxTRK&sssrc=4429486&ssuid=x_m7oh54Sk2&var=&widget_ver=artemis&media=COPY