One of my tappet covers is a bit battered and looking for a good 2nd hand one I came across this
https://www.racebase.co.uk/product/1-1-2-x-24tpi-rocker-box-tappet-cover-breather-nut-suitable-for-bsa-b25-b50-ccm-triumph-pre-unit-engines/344?cp=true&sa=false&sbp=false&q=false&category_id=24
That looks KEWL thinks I does it do anything or is it about as much use as a chocolate spark plug.