I made these a while back. 

Bits -- two 5/8" clevis pins, two lock pins, a few brass bushings (5/8" id, 3/4" od), 2 5/8" id washers, reuse the two 3/4" id washers.

Effort -- drilled out clevis pin holes to fit lock pins.  In the end, I could have just used the original bolts drilled to fit the lock pins.  Even cheaper!

Results -- working great for 3 months or so.  Still easy to unhook.  I need to make a tether for the bar to hold it up against the frame.