Flies! Help?

I have a problem with flies in the house at the moment. The only place they can be getting in is a small tear in the dining room window flyscreen. It's only about 1.5inches by .5 of an inch, but I think they're telling all their buddies about it!

I tore it last year when I opened the window on a really hot day after not having it open for almost a year and I didn't realise that there was some rolled up fencing wire which had fallen against the screen and the glass.

After I tore it I asked a friend if they could send me some fishing line to repair it. My friend has forgotten. Has anyone out there with my snail mail address got a piece of fishing line they can send me? It needs to be about two feet long, just in case! And fairly fine... The screen is perfect except for this rotten L shaped tear. (It is the same screen wire which came with the house 16 years ago!)

Thanks everyone.

Bloody flies!

Update:
Genius! In the mean time, while I sort out some fishing line (ever tried to source stainless steel screws/bolts inland? That's another story, but a similar dilemma.), I just swapped the screen with the store room window's which is the same size... yeehar!