What you are looking for is really a DRBG (deterministic random bit generator) rather than a CSPRNG, as the latter need not be reproducible or even carry observable state. DRBG's are defined to take a seed and return a stream of cryptographically secure bits based on that seed (that is, DRBG's are technically a subset of all CSPRNG's, but when people say CSPRNG they generally mean the "entropy pool" kind of nondeterministic designs).
There is nothing inside Python itself for this, as the only source of cryptographically secure bytes that Python provides is ultimately the OS's own nondeterministic generator which does not meet your needs.
You could use PyCrypto cryptographic primitives to implement a known good DRBG such as HMAC-DRBG. There is also this Github repo which implements HMAC-SHA512-DRBG with test vectors. There might also be Python bindings to crypto libraries like SSL which may provide a DRBG ready for use (though I don't know if OpenSSL's cryptographic layer provides such a thing).