HelloCustomer Welcome to justanswer!
Best place for a Porsche battery other than the dealer is at NAPA Auto Parts. I used them in 20 of my clients Porsches and had good luck. Both vehicles have had that battery for more than 3 years now. As for unhooking the battery that will work. The car has a bad module thats not turning off and is killing the battery. A parasitic draw test needs to be done or the battery left unhooked.