This is how to restock your sold out accessories for free.
When your accessories have sold out and you need to restock, click 'edit', tap on the item which needs to be restocked and select the 'box' option. This sends the accessory back into the 'shop' menu. Select 'back' then click the 'shop' menu and go to 'accessory'. Here you will find your accessory with the lable 'place' under it. Select the accessory and place it back into your store. The accessory is now completely restocked without decreasing your cash.