You must pay your state tax due using the state’s preferred method of receiving payment. For most states that will be by making a payment to the state’s own tax website, or by mailing a check or money order.
https://ttlc.intuit.com/questions/1900884-what-are-my-options-for-getting-my-state-refund-or-for-paying-any-state-taxes-i-owe
Can you purchase a money order to mail in to CA? Or can you pay by credit card? If you do not have a credit card, you could get one of those pre-paid cards for cash and then use it on the state's site to pay.