I don't grow them myself but how about chicken wire with bamboo poles put through the wire into the ground. It would be a lot firmer than string.
Take a look here http://pryorfrancis.wordpress.com/2012/04/14/pea-sticks-my-favourite-job-of-the-year/ (if you watch Timeteam you'll recognise Francis Pryor) - I've not grown peas for some years and when I did I lived in the countryside where I could get faggots of hazel pea sticks from the chaps who cut the hedges and coppiced the hazels. They are absolutely the best way of supporting peas.
Other types of twigs will do, but hazel are undoubtedly the best as they are flexible yet strong. The thing is it's probably difficult to get them at this time of year, but next winter ask around in the countryside ....
I recently cut out a load of cob nut sticks earlier on in the year, do you think I'd be able to use those Dove from above ? I have stashed them to use as plant supports if suitable.
I'd use them Peanuts - if they don't have lots of little twiggy side branches then you could get some other twiggy sticks and put them amongst the cobnut sticks to build up some layers, as in Frances Pryor's photographs. Should be fine.
Personally I use sticks/bamboo canes with netting for my peas to grow up on the allotment and it works fine
Just can't get hazel twigs