Are you talking about the netting type or just strands around the enclosure?
I bought my netting, Energiser and mains lead-out cable secondhand on ebay. If you search for Electric netting it will find stuff but keep going through the listing as you get all sorts of weird stuff - at the moment there's a good bargain right at the end of the "used" stuff. Silly bloke has got it tangled up but a bit of patience and a helper would sort it out.
Be wary of "sheep netting" as sometimes it's just lost of horizontal strands.
You could also have a look at some of the kits available - I never bothered with a gate, I just undid the clips and stpped through.
