I am part of Agile Collective (http://agilecollective.com/), a UK base web development company governed as a workers co-op. We are 7 permanent members, up from 6 when founded in 2011.
We are a company limited by shares, and we do have a structure in which we have two type of shares: member shares, one for each member, and equity shares which can be used to raise capital. Only the member shares have any voting power in governance, so contrary to what jawns said, you can have outside shareholders. We are still for profit, and do share profits with members, but the main point is that the members have the decision making power, not equity share holders. (We don't actually have any external equity share holders, but it is an interesting area for consideration if trying to raise money to expand.)