Contact your local bar association for a referral, with the caveat being you need someone to take it on contingency. Most plaintiff's attorneys routinely accept cases on contingency, the threshold being the ability to recover an amount that justifies taking it on. It's usually a question of potential recovery, something that can easily be evaluated by a competent litigator in your area.
Disclaimer: This answer is given for discussion and informational purposes only - it does not constitute legal advice and no attorney-client relationship is formed. If you are in need of legal advice or assistance you should contact a professional in your area.
Besides the referrals from the State and local Bar Associations, ask your lawyer for referrals. If you have to, ask your lawyer to help to file in pro per to get something on file to preserve your statute of limitations.
Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.
I'm surprised the attorney wanted payment up front, usually wrongful termination cases are handled on a contingency basis. Contact a plaintiff's attorney in your area immediately so they can sign you up and prepare your complaint. You can find an attorney online, the yellowpages, avvo, or through the San Diego Bar Association.