Zip ties seem to work with a couple of tesco bags inside so it sticks up .(other bags are available for 5p but I did see some one selling a used one the other day on a facebook for sale site for 3p.Used only once!)
trousers + gaffer tape/duck tape.
Mind you until you have ridden with a nylon fluffy beard you have never ridden
“We can't just drop everything, sir!"
"Mister Lipwig. Is there something in the word 'tyrant' you do not understand?”
― Terry Pratchett, Raising Steam