There is interesting information and also instructions for home-made masks here. It includes tips on how to stop your glasses steaming up and how to combine wearing masks and hearing-aids. This site includes a link to making a mask without sewing by using a T-shirt.
There are also films on YouTube showing how to make a no-sew mask from a sock here. (If you find this difficult to access, there is a film we can email to you. It is 14mb so not attached to this message.)