I am need of item no 18 being the 2 x screws that attach the muffler to the cylinder. how can i add this item ?

Thank you for your email. I have had a look for you and these are the bolts you need: https://www.lsengineers.co.uk/pan-head-self-tapping-screw-is-d5x20-stihl-part-no-9075-478-4136.html