First you need to get a clean High Density Polyethylene plastic Fuel Can ( Petrol, Diesel can ).
Step 1: Boil Water in a Kettle
Make sure you only boil tap water
Step 2: Add the Boiled Water Into the Clean Fuel Can
Put your ready boiled water into the Polyethylene hard plast Fuel can.
Step 3: Place the Clean Water Filled Container in Bed
Place HOT Water container in Bed.
Step 4: Warning
(1) Don't use a fuel container that has already been used for fuel.
(2) Do not boil Fuel
(3) Do not Mix Fuel with water
(4) Do not spill fuel on your bed
Step 5: Very Hot
The container will have a Very hot surface and will serve you for a number of years. You can wrap the hot water container with a cloth. Or you can make something you made to dress it up.
Step 6: Dressing Up
You can dress up the fuel water container with something you made or use a cloth.
Step 7: Future Manufacturing
In the future I will manufacture High density Polyethylene Dog and Cat bed containers that will hold Hot boiled water, to keep your pet warm. Even in Dog and Cat Kennels.
But the best one is to make your own bed warm with the water container.