Probably this one.
http://r4i-sdhc.com/downloade.asp
Check under "R4 SDHC kernel download (without i mark)
It does say the website on the cart in their picture but otherwise looks the same, maybe they added the website name in later batches.
What about this one? http://filetrip.net/nds-downloads/flashcart-files/download-r4-upgrade-1-27-2-f22074.html
Edit: This is the only firmware files I could find on Filetrip that seemed old enough to be for your particular R4 Upgrade. Hopefully they work.
You could try alternate loaders:Still black loading screen :\ If it helps this is the menu I remember seeing when I first got the R4
Should be this one: http://www.r4ds-ds.com/pages/R4-III-Upgrade-Kernel.html
Check if it works ^^
It's an older clone, probably from a first time cloner. This was back before everything needed to be colorful, covered in extra words, and labeled with all kinds of firmware numbers. Twas a simpler time that I look upon fondly as I remember everything I dealt with trying to help people as the years went on.That interesting. Usually R4s get kinda crazy with their labels, but this one looks relatively normal compared to the regular R4.