Bulk Reef is likely a fine source, as is this one probably OK:
http://www.buckeyefieldsupply.com/Calcium-c66.html
but it turns out quite a lot of people have used the new Dowflake with no apparent issues. We've never really known if there would be any issue from elevated bromide, we were just very cautious about it.
Here's a thread about t it:
http://www.reefcentral.com/forums/showthread.php?s=&threadid=1527547