I have not been able to find these round head bolts either. When I tear apart a frame to replace the glass and sand/buff/polish the frame pieces, I have been using "Button Head" # 8-32 x 3/8" bolts like these IF the original round head bolts are not present to reuse and have been replaced by Philips head bolts. This picture is from Menards but I have also bought them at Home Depot or Lowes where they are in the specialty hardware drawers. These hex-head bolts are not correct but SO MUCH better looking than a Phillips head bolt.
Screenshot (85) (resized).pngtop glass bolts 1 (resized).jpgtop glass bolts 2 (resized).jpg