ALternatives To Window Flashing (Tyvek Flexwrap Too Expensive)?

[SquirrelMadness]

Hi, anyone know of alternatives to Tyvek Flexwrap for window recess waterproofing?

I only need about 3m of tape and this stuff is over £120 for a 25m roll. Don't need that much.

It's a timber build and the flashing needs to be at least 100mm wide.

Thanks.