B767-300 Flight Attendant reported the transport of Li Ion battery cargo with insufficient number of containment bags.

Narrative

Prior to boarding guests for the flight; Name1 informed me that there was 6 large duffel bags that was to be brought on board the cabin by 6 Company guests. (These duffel bags and it's contents were originally placed in the cargo hold but Name2 noticed them since he was working the cargo bay with Company loading cargo.) The duffel bags were to be escorted and monitored by 1 guest each. The guests' escorts and duffel bags were placed and seated in Cabin Zone A. Each duffel bag carried approximately 6-8 lithium ion batteries the size of a laptop battery. Name1 advised that they were packaged fairly well to ensure there was no thermal runways or short circuits that could happen inflight. Apparently each battery pack was packed separately; and was contained separately by its own protective cases with the charges being tape down etc. to prevent thermal. Captain Name advised to monitor the duffle bags at all times throughout the flight. Duffle bags could not fit in overhead bins or underneath the seat due to its size. Each bag was placed (1) per middle seat; of each of middle rows; perspectively Rows #1-6 and tied down in the middle seat with multiple seat belt extensions as needed. The concern to this is the amount of [Containment Bags] available in the cabin that would be needed if in event that there was to be a cause of fire especially if more than one of these duffle bags were to have a thermal runway or short circuits of the batteries it carries. The handling of one of these duffel bags was also a concern due to its size and its weight. Unfortunately I was unable and it was unforeseen for me to take a picture or a video of the duffel bags as needed so that this can be further given a true and correct measurement/point of reference. Name1 did asked myself and Captain Name beforehand if it was alright to bring these duffel bags in the cabin for the flight. I referred to the Hazmat manual. And yes I agreed to it; so as Name at the time. We both agreed to it. At the time Name1 did advise that it should be safe; for Company assured him that the batteries were safely and protectively packaged more than usual that is why the duffel bags were huge in size. In regards to the [Containment Bags] amount onboard; please note for Aircraft X there is only 1 [Type 1] / 1 [Type2] at L1 and 1 [Type1] / 1 [Type2] at R4. There are no additional or extras on board even with the Onboard MX (Maintenance)'s supplies. Post flight; Captain Name did bring it up for he was concern; and he spoke to Name1 further more how the batteries were packaged; etc.