Having had a short conversation about this in another thread I thought I'd
put the info I found into a new one for anyone looking for the above.

Found a website www.queenswood.co.uk

Replacement cover for 2 tier mini greenhouse £6.99
Replacement cover for 3 tier mini greenhouse £7.99
Replacement cover for 4 tier mini greenhouse £9.99

All found on this link http://tinyurl.com/2x2qr

Hope this helps

Shannie