Yeah thats what I thought as well, but wanted to check first. There was only tray versions for the Intel cpus I mentioned so it seems like those are meant for oems. And I couldn't find the 2200ge (only the g) on newegg or amazon.There are some NUCs from Shuttle, Zotac, ECS that are smaller and possibly cheaper than building your own, including fanless models. I've seen Shuttle models with COM ports, not sure about the others. Check Zotac Zbox, ECS Liva, and Shuttle.
Don't most motherboards have the pins on them for serial ports?ITX motherboards with decent processors and built in serial ports seem to be hard to find. However, I did find add-in cards. You can add normal PCIe cards to ITX, or a card like this to boards as small as STX: https://m.newegg.com/products/9SIAC5C70U2597
Edit: Probably NUCs too.