Unfortunately once you already have a plan with Public Mobile it becomes a bit limiting as far as what plans you can then change to. The only surefire way he could get a plan open to the general public but not available on his account would be to cancel his existing subscription and set up an entirely new account and then select the plan that he would like.
Alternatively some people have been successful in looking at what plan changes are available and then lowering it each billing cycle until the plan they actually want becomes available. This can be time consuming though as you make 1 change per cycle and I'm not sure if it truly guarantees that his targeted plan eventually shows up as an option to switch to.
