LJCycle: Plastic sheeting?

[friend_of_tofu]

The old owners of the house abandoned a larger mini-greenhouse structure, with its shelves but without its plastic cover. It's a bit tatty, held together with gaffer tape but basically sturdy. However, we have nothing to cover it with. I wanted to keep the plastic cover form our mattress when we first moved in, but we were drowning in crap and had to throw it away. I've regretted it ever since, especially since the mini-greenhouse covers I've found to buy in garden centres are all for the smaller sized ones. I also don't want to spend much money on it as it's fairly old and manky, but I would like to use it if possible - waste not, want not, and all that.

So;

1) Does anyone have any LARGE pieces of unwanted, fairly sturdy clear plastic? Mattress covers are ideal, but other large purchases may come in something suitable?

or

2) Any idea where I can buy plastic sheeting v v cheaply? I am thinking I could maybe acquire a few metres, cut it up and bind it together with more tape.

Thoughts?