Cajun Bandit makes a ring, as does EZ Que (although i think they're out of business, you can still find the rotisserie on ebay)
The cajun bandit rotisserie will fit a weber kettle AND a WSM, whereas the weber rotisserie ring will only fit a kettle.
The cajun bandit ring is also a lot more airtight than the weber ring, which helps a lot in my opinion.
