Tony, I know exactly how you feel; I had a favorite kind of fingerpick that just dropped off the face of the earth a few years back. I've had to adapt to National metals, but there are some things I just can't do with them — like a brush down with my index finger. The plastic picks I liked flaired out at the end, but the curve of the Nationals just yanks them off and fires them into the sound hole.
Just a thought on the picks you've found that substitute, but don't fit well; have you tried putting the picks in boiling water or in those heated beads an optomitrist uses for glasses frames and bending them to fit your thumbs? I've done that in the past and it can make a world of difference in comfort and/or holding power.