How do you find people who will be there for you
It is so hard for someone who built so many thick barriers to other people and walkd away from anyone who could have helped them now to find out that they need to let someone in to help them deal with their life. someone that can be let through those walls and can provide the kind of help that is needed in the moment.
How do people find those supportive, available people?
Dear @orangeMaple42
I agree with what you said about finding genuinely supportive, an amazingly caring people. It's truly difficult, because we don't know how supportive or caring a person can be unless we get to know that person for some time.
For some time in my life, I desired that sort of person to be there for me as well.
I wanted that sort of person so bad, I ended up being that person for someone else who needs it.
Then I realized, this world revolves around the act of giving and taking, when I started being that person for someone else, at the time when I needed the same support again, the other person whom I was there for became the one for me too.
Perhaps you could be that person, for yourself, for others. As the Beatles once said,'And in the end, the love you take, is equal to the love you make', so perhaps the right one to be there for you will appear then.
But of course, this is just a suggestion. And I think for everyone, the way find this type of amazing people is different, because we all lead, similar, but significantly different lives. Maybe you could start by befriending new people, explore new things and expand your horizon. As you have shut yourself off for some time, maybe its time for you to see new things, since you've already courageously shown your initiative by sharing your story here. 
Of course, these things may take time, but it's alright if you haven't meet the right person yet. You just have to continue searching, as you never know when the next shooting star will appear in your darkest night.
Yours sincerely,
Snow 