They are very hard/impossible to find, no NOS out there, no used on ebay, nothing!
I was able to get them from a member here, they are used and brittle/cracking, but they get the job done and look good, returns that factory/stock look.
I did try a repro version from classic industries:
http://www.classicindustries.com/product/1977/truck/parts/fp72017.html (also sold at summit, and cheaper)
And they were weird, color was way off and looked like something had gone wrong in production with the rubber. Maybe other colors would be better, but I had to return them.
Here's what those Repro one looked like:
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And here's my current setup in the 'burb with factory mats:
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Nighttime shot, you can see I added 2 extra footwell/courtesy lights for extra lighting (opposed to the original single light in the middle as is stock) - I spliced into existing wiring so all lights trigger with door ajar and headlight switch turning on.