NJ taxes public retirement plan contributions, health insurance, Flexible Spending, Health Savings Accounts, and more. Because its supposed to be taxed, you can't really avoid this. Everyone with a 457(b) or 403(b) is taxed for NJ purposes.
When you begin to receive distributions, they will be reported on Form 1099-R. On your NJ tax return, you will recover your contributions tax free. You will either be taxed using the Three Year Rule or the General Rule, which you will determine when you start collecting the retirement. Either way, you will not pay taxes on your contributions again.
You can see some info starting on page 4-
Whether you use General Rule or Three Year may depend on how much you will collect in comparison with your contributions, and whether your employer (aka the NJ government) also contributed.
But, no, there's nothing you can do to avoid being taxed on the contributions now. That is simply a fact of NJ taxation.