I mentioned mysql-connector as an example of a complex enough library that runs with gevent via monkey patching (in reply to "gevent only solves the most simple conversions by monkey patching", which is wrong).
Have you tried gevent-MySQL? It's written in Cython and as far as I know is fast.
A while back we avoided gevent because of this but used eventlet instead because they had a native MySQL patched driver.
Performance on the pure connector was just too bad.