Hi Ana,
I think Patrick of Zill.net offers shared. You can look at the community page for hosting options
https://openacs.org/community/
I would recommend zill and acorn, I had very good experience with them. They are nice small shops and the level of service is still personal and prompt. I had a bad experience from a mid size shop. I did have good exprience from bigger size shops like Globix, although I don't think they will offer shared hosting of OpenACS. Good luck.