You can get adhesive shoes but I think they're quite expensive, my farrier uses them for some laminitics he shoes and he showed them to me once.  Keratex do a good hoof hardner, I think their products are devised by farriers and are quite good.

His backs are only bad from walking on stones and concrete without shoes but i cant shoe him because of his hoofs its a viscious circle!

I have heard of this (was with a farrier for 6 years lol) I had a mare whoz hoof wall was thin and you ran the risk of pricking her (nail goes though white line in hoof and is very painful and can put a horse off being shod again so you then cause another problem) I put her on farriers formula which is a hoof supplement (there are lots but the cheaper ones just dont do anything and you are wasting money)it strenthed her feet no end and she was find to be shod, your farrier is acutally doing the best thing in his mind as he would be getting alot more money if he was shoeing your horse, most farriers would just shoe her anyway risking pricking your horse which can/will cause allsorts of problems and possible vet bills, he also risks losing custom and most owners dont like what they say if they are honest and will just go to another farrier who will just do the job no matter what. If your horse has bad feet which can be from bad breeding and they might never get much better why dont you invest in some old mac boots so you can ride her without her going lame or foot sore and in the long run they are cheaper then shoeing every 8 weeks. talk to farrier about using farriers formula or using old mac boots.