I don't think you'll have much luck finding a glass bulkhead. You could probably design it yourself and take the plan to someone who will make it. Sounds expensive.
Consider putting up a small greenhouse around the basement steps - so instead of a bulkhead, you have more of a canopy or bubble that you enter through. It will probably cost less - and if you get one that's just slightly larger than the stairwell, you'll have room for some plants.