Old Leafsprung Land Rovers

I bought a 'new' old stock geniune land rover 3/4 tilt (still with the tear off cardboard Land rover tag sewn into the bottom) for my 109 for £200 quid from fleabay just before xmas and with hindsight I wish I'd paid a little extra and got a proper new one rather than old stock.  The canvas is fine but the plastic windows have yellowed with age and where they've been folded in storage there is a crease in the plastic which I thought would relax out when opened up.  It hasnt :-( and the cold weather over the winter has started to split the windows along the fold, the split is only 1/16" inch at the minute but I know it's going to get bigger.  Looks like I'll need to find a camping/marine/automotive canvas repair place for new windows at some point! ****.