At this time the staff of Water Testing Blog does not know of a simple testing method for bromates. This does not mean companies who bottle water cannot have their product(s) tested for bromates.
“MWH Labs has received accreditation for testing of bromate by EPA Method 317 under the Stage 2 Disinfection/Disinfection Byproducts (DDBP) Rule. Method 317 is, a very accurate and very precise analytical method for bromate, that avoids many of the problems with false negatives and false positives that are associated with the existing analytical method (EPA 300.1). Additionally method 317 is capable of detecting bromate as low as 1 ppb (vs 5 ppb for method 300.1), helping clients to more accurately assess their bromate treatment options. Bromate is regulated in bottled water and potable water at a level of 10 ppb.”(source)