Small plastic fasteners which slide onto frame holding storm window in place

Summerville Aluminum in NJ custom made a storm window frame and window which fits over old single pane picture window on my home; the window pane is secured with small plastic holders which slide into the grove where the window sits thereby holding it securely; the last holder broke and the painter tossed it so I don't have one for a picture; but, here is a picture of the front and rear picture windows needing fasteners,