Awning advice

I would at least go to a dealer to get some idea of what is available, full, porch, pole (lightweight or steel) air... 

If you already know all that then do you want new or second hand? if new then either a local caravan dealer, online, or order direct from the manufacturer. Buying from a dealer may mean you'll get better advice and if things go wrong perhaps easier to get things put right. Awnings are heavy things to send through the post.

If second hand then some dealers may have those or look out for adverts in caravan magazines or even local adverts.

Dealers sell second hand as well as new.
Depends on your caravan, you need to get the measurmenets and buy to suit your unit and budget.

 It would help to know where you are based.

If you are anywhere near them, Glossop Caravans have a good range of awnings with quite a few on display.

It would help to know if it’s for a caravan or motorhome.