as others have said the fire brigade may help. they are always very keen to ensure that Joe public is safe and so if they were concerned that you don't have a working one (battery flat) they will likely help.
our local brigade is coming out (after lockdown) to do a full safety inspection (it is a huge stately home) and they are doing this free (though the owners of the property - my employers - will give a donation afterwards)
My son has just left. No more beeping. Thank God!!! I’m sitting in my bedroom to allow the fresh air from my open living room window banish the germs. He was masked up though.
I had some lovely men from the fire service come round, they even came in a fire engine. The main idea was to help in terms of a plan should there be a fire emergency, with my disabilities. They fitted me new fire alarms, which sound like the ones alavahaf mentioned.
I got some nice boxes of biscuits and other treats in to give them to take back to the station as a thank you, partly as it's a free service, and just as a general thank you for all they do.