Can’t find “lorry covers” on the web?  Try searching for “tonneau covers”. 
Tonneau is from a French word and is pronounced as “ta’ -no”.  It is commonly used to describe a bed cover for a pickup truck.  To get a bead which kind of tonneau cover is appropriate, check it out with the manufacturers online. 

Current users are mostly professional Landscapers, Movers and Construction companies.  They install tonneau covers on their trucks to shield their equipment from the elements of the weather and for extra protection against theft.