Made my own b-screw for my Tiagra RD 4400-GS. The flat step on my frame's derailleur hanger was too far around for the stock b-screw to catch, so I went to the hardware store for a longer M4 screw, with a wider head, plus two nuts for it. I screwed one nut up tight against the new screw head, then put the screw in
the wrong way, and snugged the other nut up against the the derailleur tab, right where the old b-screw head would have been.
Like this:
b-screw solution
Now the upper roller pulley is kept out of the cogs, otherwise the derailleur would have been unusable on this frame.