Prevent toilet backflow

A question about : Prevent toilet backflow

On the odd occasion when we have had torrential rain the downstairs toilet 'gurgles' presumably as a result of excess flow through the drains. We are worried this may lead to back-flow in the toilet. I have been told there are a number of devices that can prevent back-flow from a toilet in this event. Can anyone point me to a temporary device that can be fitted to prevent back-flow? I have found a couple on the internet but they seem expensive for what they do.

Best answers:

• a ballon or maybe clingfilm ?
• Thanks for the replies. I am not sure if it breaks the rules but here are a couple of links to the devices I mention:
  https://www.ebay.co.uk/itm/Medium-Toi...item3a704f2687
  https://www.floodingsolutions.co.uk/shop/toilet-panseal
• Thanks. Two questions then:
  1. Do you live on a floodplain and is your area high risk?
  2. If the answer to 1. is yes what does your water/sewerage company recommend?
  If the answer to 1 is no you have a non problem IMHO.
  Cheers
• Waste of money by the time the foul drain would have backed up enough to flow out of your toilet your whole street will be under a couple foot of water
• Thank you for the most entertaining replies which have given me many minutes of enjoyment. You're right some of these products are jumping on the 'flood risk' bandwagon and the prices they ask are extraordinary. Perhaps, in an emergency, the best option is to ram x meters of roll down the loo in the hope that it blocks it :-)
• I don't think you need to do anything for the reasons above, however if you still want something you an use anti-rat fittings in the soil pipe.
  Remove the toilet, ram the device in the soil pipe and replace the toilet.
  They are used to stop rats crawling up the soil pipe from sewer.
  We have used these to prevent backflow due to 2 toilets sharing a soil pipe on the same level.
  They only cost a few quid
• Oh, just realised this is in the flood sub forum. These rat devices are good for stopping backflow and waste reappearing in the pan. I don't think they are watertight for flood issues