I can't believe no one has mentioned Rainbow (sp?). Expensive but no bags, no filters of any kind. We have had one for probably 20 years and have had NO problems. It uses water as the filter agent. Exactly how it works, I don't know, but it works well.
If you look up the price of one, be sitting down. That said, if something went wrong with ours we would buy another without question.

PaulM

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84 500 SEL (307,xxx miles)