I have done several unpaid internships in my career. Not just in IM, but in the "real world."
No, they weren't "official" internships. I simply offered my help to people that I wanted to learn from.
Was it glamorous? No. I did the grunt work. I did the stuff that nobody else wanted to do.
But in doing so I learned more in those internships that I had entire time I was in college.
I have had the privilege of learning from some very incredible people. Some of those people that I interned for I developed friendships with.
By humbling myself and offering to help in whatever capacity I could, I got more experience, knowledge, and advice than I ever could have hoped for from a paid mentor.
Figure out what kind of services you can offer to someone. Do some reading. Find people with success on this forum - they aren't hard to find if you do your homework.
Maybe it's writing. Maybe it's graphics. Maybe it's just being a virtual assistant.
Instead of approaching the situation from a point of "I want free help from you, and you should give it to me" - turn things around.
"I want to offer my assistance to you, however you need it, so that I can learn from you."
It is a very significant difference in mindset, attitude, and approach.
Offer something of value - yourself, your skills, and your time - and you will get many times that in return.