Is there anything to put in large fire escape gratings to make them heel friendly?

It will depend on the building and fire regulations for your area. Fire escapes are made to a specific spec and whilst shoes with heels are an issue the only option is to weld checker plate across the step but not the riser. However, checker plate can become slippery in time with weathering and potential algae so that is why the steps are made from open grating materials thus allowing for grip especially in wet and frosty weather. In most cases H&S and fire regs will request that the shoes are removed when leaving the building to aim more appropriate footing as they will insist that shoes with heels cannot be run or walked quickly when wore in a safe way.