I’m not an expert in the precise nature of what you’re trying to do, but I found numerous cards that appear to do what you want by just typing “PCI-e to usb-c” into Google.
Newegg seems to have the exact item you’re looking for, priced at $40.
That’s what I originally thought, but, the problem is, unless the card (the port, actually) specifies a capacity for DP alt mode, the connection will not provide video through, say, a HDMI adapter or a hub that connects via USB-C. I have multiple hubs, including one from Dell, with HDMI output that works if plugged into the USB-C (DP) port on my laptop. Try the same thing with the USB-C port on my desktop (which is not USB-C DP capable) and the same hubs fail to provide output from their HDMI ports. Most of the expansion cards sellers specify, if you dig deeply enough, that their card (s) USB-C ports do not provide DP alt mode.
Now, If you’ve found an expansion card for $40 that DOES provide DP alt mode, that’s great. But I’ve started looking through the cards on New Egg (they have quite a selection at $40 or less) and so far, no dice.
This card, for example, won’t do the job:
https://www.newegg.com/p/17Z-00VP-00001?Item=9SIAMZWBZB3194
This one, for $92 will:
https://www.newegg.com/p/17Z-00A0-001A5
But dang, the laptop was a $120 refurb...
However, your link to New Egg IS useful, as I can find specific card models there that might in turn show up used on eBay. Previously I’d only found two such models on Amazon and they were in the $170 plus range. :-(
Looking over that $92 card, it goes the other extreme and offers way more capability than what I need, or would ever need. It’s impressive tho’!
https://www.newegg.com/p/17Z-00A0-001A5