This probably is the craziest "hack" of them all, but my mom swears that if anything battery operated doesn't work with a new or charged battery, to put it in the freezer for a few hours, then try it. I am just sharing this with you, not sure if I would try it on a Clarisonic or not.
Seems like Clarisonic could offer some suggestions as to what you could do, it's a shame to have two expensive products and not be able to use them. Maybe you could contact them again and ask for a recommendation. Sometimes it depends on who you talk to.
As far as knock off products, I have not tried any of the devices, but I do order Sonimart brush heads from Amazon and they are the same to me. I won't pay for the expensive Clarisonic brush heads again.
Good luck!