Sportingbet Australia don't offer prices on all ATP events, just the bigger ones.

They do have the account opening bonus you described though, as do Sportsbet Australia (20%) and IASbet (10% plus free bet I think) None of them are what I'd really call tennis specialists, but it's worth opening an account for the bonuses.

There are ads for these bonuses on this site and if you click on the ads they take you through.