Availability of dummy power upgrade kit for PA-1

[MopacMan]

I purchased a dummy Williams PA-1, with the intent to upgrade it to a powered unit.  It appears to be an early Williams product.  Are there still available dummy upgrade kits available for older units, like this? If so, from where?  I have had no luck locating anything on Ebay.  If available, are dummy upgrade kits compatible for other 6 wheel Williams products (SD45, SD90)?