Unless you have a full length zipper (which you clearly do not), your machine was not meant to take disposable bags. You CAN, however, adapt your machine to use disposable bags - you'll need the fill tube assembly and a new cloth outer bag with full length zipper. Or, you could visit a local vac shop. Most vac shops throw away Kirbys that old. They have virtually no resale value to a vac shop. It shouldn't be too hard to convince them to give you an entire bag/sani emptor assembly (complete with fill tube) off a Heritage they're going to dispose of.