After buying both fabric and disposable masks I still had issues with glasses fogging up and also generally with breathlessness. It was time to rethink.
I took two squares of soft, pure cotton fabric from one of our Forgotten Cotton duvet covers and stitched them together, inserting darts in the centre of the top of the mask to allow for “nose space”. Then I put in two darts on each side edge of the mask to reduce gaps at the side. Elastic hair ties worked really well for holding it in place at my ears, being nice and fine. I stitched the two bottom corners together to make it a snug fit under my chin leaving s small exit for breath to escape downwards.
When wearing, the mask is just long enough for the bottom of the mask to tuck into the neck of my coat. Combined with the snug fit, this allows the exhaled air to go down into the coat instead of up towards my glasses.
It also gives a little extra breathing space.
I hope someone finds this useful