There isn’t one because of how BA works. Unlike most airlines reward seats do not have a dedicated GDS bucket so most systems cannot see it.

Reward Flight Finder is similar but updates a lot less often (daily vs hourly in my observations). If you are looking for super peak dates then you need SeatSpy (eg half term seats). If your needs are vaguer, eg Barbados on any dates in Oct or Nov, then RFF may do.