I made one when I could not locate an original or repro, used a 70's sissy bar to do it Think it was a little longer than the OG. In this thread there are pics and info on what i did as a quick and easy to make it fit. I had also sent that original seat to kenny so he could pattern it for other members (pre dates Karen making seats by a few years) I dont know if Kenny is still doing seats or not but he posted in that thread so you can find his info in there as well.....Karen may have a pattern now too I am not sure. Link is below the pic when the
bike had the MC sissy bar on it still:
https://oldminibikes.com/forum/index.php?threads/1974-jc-penney-duster-chopper-cat.51788/