Frontera 2.5TD San Diego Front Hubs

OK, looks like the hubs have gone. Whenever you engage 4x4 it makes an awfull grinding sound. When in 2x4 it is not nearly as bad but still there, specially when turning. It started off not so loud, but then rapidly got worse - over about three days. Anybody know where I can maybe get a pair of these things? Don't need to go for new, second hand would be great.