The ONLY place I have been able to find refills is at Amazon, no "brick and mortar" seem to. There are "snap to fit" options and there are specific lengths. Pay attention to the groove width. One time I was buying for a 66 Bronco (original arms), I was in doubt (or maybe confused by all the options) I think I bought 4 sets to be sure to get at least one right. Ironic that I cared, as its a topless "roadster", and has non functioning vacuum motors, but wanted a completed look.
Not even Rock Auto seemed to have refills, unless I didnt know how to find them. (I was actually looking this week, for another vehicle).