You have to get the Member's Pass, now only available by hacking.
pancakes
it is in veilstone city
hearthome city
It is in Sunyshore City.
Go to Veilstone city.
use the item finder thing near the hotel it should be there.
Petalburg City is not in Pokemon Platinum.
You will find the Pokemon Electabuzz near Sunnyshore City. It will be on the road next to Lake Valor Hotel and Restaurant. I hope this info helped!
From Veilstone, after you beat it's gym leader Maylene, you head south to lake Valor. When you get to the Valor lakefront, go to the hotel. In the back of the hotel is an exit that leads to Pastoria city.
You can find a Shell Bell at Hearthome City in Pokemon Platinum.
below hearthome city
Hearthome city.
In Pokemon Platinum, Diamond, and Pearl, the department store is is Veilstone city.
Eterna City
hearthome city
pancakes
In Shunishoart City.