I have secured a source for 1" thick PVC material, however it is both difficult to get AND more expensive than the 3/4" material. Getting this material is about a 1-hour trip for me beyond where I work (already a 1-hour drive each way) and the cost is more than double the cost of the 3/4" PVC material. HOWEVER, I have enough to make roughly 10 sets. Cost will be $45 per pair, shipped.
I do not recommend this unless you need the extra depth. The thicker depth may require filing and/or trimming of the inside of your door panel and/or minor filing of the adapters. I never tested the 1" adapters in any vehicles (but several Forester, Legacy, and Impreza owners HAVE used stacked versions of my 1/4" adapters and my 3/4" PVC adapters to gain more depth), so I have to issue that disclaimer.
Price: $45 shipped per pair in the US.
For more info about my spacers in general, see the links in my signature below.