I hope you can find an invite, but why do you want to get in there? Correct me if I am wrong, but from what I heard they don't really have exclusive content, the big upside to Bib is that content is well organized and what you download from there is always good quality. But you can find that content from different sources, it just takes a slightly more effort, more tries. If you are interested in where you can get ebooks from, then PM me and we can discuss. If you are interested in audiobooks, Bib is a bad place for them, because downloading them is hard, since you need to build a lot of buffer from ebooks to be able to afford downloading a single one. I can also direct you to sources from where you can get audiobooks if that is what you are after. And a big majority of Bib's content was leaked two years ago, although that's offline atm, it should be back up soon. So don't get me wrong, of course it would be nice to have a Bib account, but it isn't 'the' tracker that you can't live without.
If you still really badly want it, you can follow@Achelous's advice: you can purchase a baconBits invite from the member shop (it's available, if you upgrade to VIP, it's even cheaper!) and be active there, rank up and try to get an invite from there. If you don't like that specific tracker, take a look here:
All I am trying to say is that you have options to get in there if you really want, you are not at the mercy of an invite you most likely won't get.
Anyway, good luck finding an invite! And keep collecting points, maybe it will be available in the shop in the future, but it's not a cheap invite!