When I see a Bb(b13) in a chart, I would assume (as most players would) that it includes both perfect 5th and minor 6th (or 13th), which is kind of unusual sounding chord.
If you meant a major triad where the minor 6th replaces the perfect 5th, then it's just an augmented chord (1, 3, #5) that is available in iReal chord library (noted with the symbol "+")