I'm looking to create a raw transaction, to then sign it and broadcast it using the eth.sendRawTransaction rpc method.

I'M LOOKING TO DO THIS OFFLINE, ON CODE, USING AN OPEN SOURCE LIBRARY. OR ONLINE BUT WITHOUT USING ANY ADDITIONAL WALLET.

I see there is no RPC method to create or sign the raw transaction. I can´t find any libs to do this (offline) either. 

Any help or guidance on how this could be achieved would be most thanked.