I checked at Performance and found them doing a search under "kleen wheels" (top left of the home page). Once the page comes up, do a search for your particular make and it'll promt you from there.

I searched for a 1980 300-D (123 series) and they are available. The prices range from approx. $30- $65. Didn't go far enough to see what the price was for the 123.

Hope this helps.