Looks like it's time to make a solution ... and then fix the fence on my large table saw sled.
Step 1: The Parts and Layout
Sorry, I got distracted. We'll focus on the modification. 1/2" plywood which I cut down to 10 1/4" x 18". A strip of 3/16" hardboard cut to 1 3/4" wide (left it long). and another piece of 1/2" ply that was 1" wide and around 10 1/2" long (left it long).
The offset to the left of my circular saw blade is 5" so I scored a shallow line at 5 1/8" on a table saw. I'd recommend going a little more then the offset for a cleaner first cut (I know I should've gone with 5 1/4"). This shallow line is an alignment line and a trick I found on youtube.
Step 2: Glue and Screw the Rail
Step 3: Cut the Edge and Attach the Stop
Now the modification. We want to attach a stop to the bottom of this board and we want it to be square. Turns out my framing square ... wasn't so square, so it failed at its only job in life. I used a speed square, which actually did its job, but you could use a combination square or a framing square that doesn't suck.
I lucked out and this end was already square so I used my table saw fence to help me keep it all flush while I slapped on some glue, fired a few pin nails and then secured it all with a few wood screws. I trimmed off the excess on the tablesaw at this time.
Step 4: Brand It
Step 5: Ready to Cut
What makes it better than the plastic version I could buy for $13? I can throw a clamp on this and the weight of the saw is supported the entire length of the cut, so Ican run the saw with my left hand while supporting the off cut with my right hand, which eliminates pinching/kickback risk I'd normally encounter. Also, since the offset to the blade is already calculated into the track, I don't have to measure my saw shoe every time (because I forget the offset) and add to my measurement, etc. Just mark my desired cut position and put the track there. It also didn't cost me $13.