I require grade B impact protection, but I am unable to find any safety spectacles to that requirement, can you help?

The European Standard does not allow for safety spectacles to be tested and certified for grade B impact resistance. 

Impact resistance is tested by firing 6mm steel ball bearings at varying speeds appropriate to the type and marking. 

Grade B impact is tested at 120m/s (270mph) which is only applicable to goggles and face shields, whereas safety spectacles have a maximum rating of F (45m/s). 

Faceshields have a maximum rating of A (190m/s). S, for increased or minimum robustness, is the lowest-rated impact marking and generally only applies to mesh protectors.