Does aanyone know of a list broker or service that will rent/sell email lists for yoga enthusiats?

Mailing lists for every activity, interest, etc. are available from scores of vendors.

See, for example, this search results page:
http://www.google.com/search?hl=en&q=%22mailing+list%22yoga&btnG=Google+Search

Not only will you find some in the hits, but the ads off to the right will be providers also.