Availability of a simple limited PRNG algorithm I am in need of a really simple limited PRNG, that either exists or can easily be created in virtually any language on any platform.  It takes only the initial seed, and is only expected to generate a small amount of output in its lifetime, normally 32-64 bytes but potentially more with very low probability.  It will not reseed.  There is precisely one consumer of its output - an ECDH key generator.  If given the same initial seed on different languages or platforms, the PRNG must generate the same exact output.  (Hence, given the same initial seed on different languages or platforms, it is possible to determinstically recreate the same ECDH keypair.)

The requirement for cross-platform consistency and no need for reseeding are driving me to seek a well known standard implementation of some standard PRNG.  It will not be Yarrow or Fortuna because they obviously don't fit the requirements.

Does there exist some well known PRNG that fits this description?

Note:  I removed "My Simple Limited PRNG" as it is no longer relevant.  Because the answer to the first question "Does something like this already exist, that is well known" is yes.
Yes.  This paper on nist.gov gives five such PRNGs.

Three of them are based on hash functions and two of them are based on block ciphers.