Guy, this is something that has been debated long and hard and the general consensus is use the old rubber. I put a new screen in my 80 and even the fitter said use the old one. But likely as not you'll need to seal with butyl.
Karl will have screens for sure. That chip never bothered me, but if I'd known, I'd have got one for you from Karl and put it in the boot. You either get new on the insurance or from a breaker. Karl's really your man.
Of course again if we'd been smarter we could have done it on the insurance before I cancelled. Doh.