Depending if you are have spare money, get some supair bunkers. Might be an idea to contact some of the larger tournaments organisers incase they are getting new bunkers and thus ditching their own. You can buy them new as well, would work out if you and some friends club together.
If not, plastic water drums, planks of wood nailed to stakes are options, depends what sort of field you want. Just be aware of public rights of way and where overshoot balls will travel to.