Ah... Good luck. I didn't think mesh was that hard either
Ebay is great for cable ties though! 99p for 100 including delivery so thats sorted for you. I can't believe our local garden centre has mesh and then someone with a B&Q within reasonable driving distance can't get it... We went to B&Q recently and it took 2 hours to drive there lol
Fixing the mesh should be easy though, even if its difficult to get the mesh. Oh and er... One note that I don't generally advertise but might help you, mesh doesn't have to be the orthodox stuff from B&Q e.t.c.
When we planned our syrians bin cage we knew we'd struggle for items, couldn't get mesh (the garden centre needs a car and we didn't have access to one at the time) and couldn't find it online sensibly so we went with making do more than most would.
Scamp's bin cage actually used to be meshed with morrisons cooling racks that we'd normally use to let cakes cool lol. I checked the bar spacing and it *just* works for an adult syrian, so we went for it. Am sure there'll be other options for mesh too, we just need to think of them...