Found the following sizes used on another forum: 3/32" x 1.5", and 3/16" x 1". I'm just going to get a bunch of both and see what works best.
I just did this fix tonight. 3/32" x 1.5" was in fact the best size.
Total time to do the Cotter-pin fix - 30 mins. Works like a charm. Total cost $2.99 for cotter-pin kit from autozone.
While 30 minutes may have been your personal best, I don't think that it is a realistic time to convey to everyone else. I would say expect to spend at least 1 to 1.5 hours on this job. It's not difficult, but it's not a 30 minute job. In my opinion, the estimates below are pretty aggressive, especially for someone who hasn't removed the door panel eleventy billion times.
05 min: Remove door panel and vapor barrier
03 min: Remove window bolts and tape window
05 min: Remove window regulator, 6 bolts plus worm gear clips
05 min: Bend end of regulator track and remove bracket from track
10 min: Modify bracket, including drilling rivet and cutting plastic
05 min: Identify best drill bit and drill two holes for cotter pins
05 min: Identify best cotter pins and position on worm gearbracket
05 min: Put bracket back on track, will require window switch to position drive
03 min: Bend end bracket
02 min: Reinstall window regulator, motor, and worm gear clips
05 min: Attach window and adjust glass
05 min: Install vapor barrier and door panel