You are doing everything right, but the funny thing I noticed working in this field, is that our there is full of people looking for programmers and programmers looking for projects. What I would suggest you is not use the channels you think are right, but to look for the channels the programmers actually use to find a job. Make a quick search on which channels are usually used by programmers to get a job, the social groups or meetups they usually use, and there you will find your co-founder.