Where to get OpenSSL binary for Android?
Your best bet will be to build it from source.

There are a few StackOverflow questions that you might want to reference if you haven't already.

How to use openSSL Library in the ANDROID application

How to build OpenSSL on Android/Linux ?

Openssl Build Issue with Android NDK r8

The first SO has an answer linking to a GitHub project android-external-openssl.  I would suggest trying to work with this code as a starting point.