Adding a Garden Spade, and Digging Bar to my gardening tool is on my list tobuy as soon as I can find them. Are they usually in a well stocked garden section? You mentioned Harbor Freight
I love shopping there, I will have to have a look around.
EDIT: You motivated me to see what I could come up with, so I went digging around way back deep in the garden shed to see if I could find an old garden tool to modify for this use and found this. It was all rusted up so a sanded and painted it. It is missing its D handle but I am scheming to see what I can come up with on that. I hope it will do fine with my SDC although it may be a bit wide. I am pleased you motivated my to dig deeper and get an old tool cleaned up ready for some use.