There are a few resources on Wikipedia, but you'd have to be quite lucky indeed to have a domain that's a plain vanilla English word, common enough to appear here.
You could use the keyword typo generator tool, or something like it, then laboriously enter each one into Google -- which ironically will try to fix your spelling -- then use the "search instead for {misspelled version}" and see how many search results you get for that specific misspelling:
Showing results for treatise
Search instead for tretise
That provides about 117,000 results for "tretise" vs. 17,800,000 results for "treatise". So you now have some idea how common that misspelling is on the whole of the Internet! So you can favor the misspellings that occur more often in the real world.
Perhaps most importantly, I also found these pages:
http://how-to-spell.net/treatise
How to spell treatise?
Correct: treatise.
Common misspellings:
tretise - 100%
Which apparently does use actual data!
We have collected misspelling percentages from nearly 15,423,252 spell check sessions on spellchecker.net website (Jan 2010 - Jun 2012).
Ideally I'd love it if Google shared data on misspellings, since I suspect they have a ton more data.. but I'm not sure if they're willing to share, maybe they view automatic spelling correction of mistyped search terms as a competitive advantage.
Would be awesome though if they did!