Tethering a Polytunnel?

Collected it today, very happy! It' 3x2m so a bit smaller than expected but it will fit better into the space that way.

It's a metal frame, a bit rusty but plenty of life left. The cover however is aftermarket, one of the green mesh zip up types and the 'door' is basically both of the short sides repeatedly, vertically slashed to create like fly strips. The cover is not in good condition but it was free so wont moan.

So, do I fit a doorframe/door and wrap it in polythene, or buy a fitted replacement cover? The current one will certainly make an emergency spare.