You pretty much already have your answers here but for what it’s worth....it’s 2021 now. If I were to buy a new flasher in today’s market, if it weren’t a digital screen, it would have to have a brushless motor and a lithium battery. The battery part can be remedied with an “aftermarket upgrade” but I would definitely make sure the motor was brushless. There is no point in dealing with brushed motors in 2021 unless you absolutely have to.