I did find totally soy-free prenatals. They were also GF, peanut-free, papaya-free, and carrot-free. They were in the Citranatal family and might've just been their standard plain variety (Citranatal Rx). No DHA--it was a soy issue, though, not peanut. And they were prescription-only. I last called in 2011, though.
If you are just needing PN, you'd probably be able to find OTC.
At the very least, I'd be taking folic acid.