snap in white vinyl glazing bead

I am needing to replace some of my window glazing bead it is on inside of windows. One side measures 9/16 inch and the other side is 5/8 inch.The picture shows it from the end so you can see the shape I know it comes in 6 foot sections the flat side is on top of window and the curved side is the side that snaps in.There is 3/4 inch space from one edge to other edge.Any help uyou can give me will be greatly appreciated.
Thank you,
Sandra