What you are looking for is a9"x6" glass insert or door lite for a steel door. It comes as a unit--outside plastic frame sealed to the glass and then an inside plastic frame screwed into the outside frame. There are a number of different manufacturers and each had a slightly different profile on their trim or frame, so trying to replace just the inside frame is going to be impossible. The screw holes are not going to line up to the outside frame studs. No one will have them in stock as that is something that normally comes with the door from the wholesale supplier.
ODL is a brand that was very popular, but their website shows a lot of fancy style glass. The RSL website below at least has information about the different types of glass etc and actually has installation instructions under their marketing header. Therma-tru has their own brand of glass inserts (TS296) and could be ordered through Lowes. You have to go there knowing what you are looking for as their salesmen may or may not know much about them. Their Reli A Built door probably uses ODL or RSL glass inserts, and they should be able to order them without having to buy the door, but its getting a salesperson that knows what it is you are looking for. Bull run may be able to help you better than Lowes as their salespeople are more familiar with the products
Home Depot has Jeld-win doors and they could order the glass inserts as well. Again you have to know what you are looking for. Again, none of them will have this in stock.
Im not sure what they will cost as I have been out of the door business for a while. I used to use a small flexibile putty knife to work the outside frame loose from the steel door as there is a sealant that makes it weather tight. The RSL site says to push on the glass from the inside once you remove the inside frame. Its not that difficult to remove them once that seal is broken.
Bull Run Lumber & Mill Work
7614 Centreville Road, Manassas VA