After buying a couple of cards of inserts from different sources, I despaired of finding front sight inserts with fine x-hairs. The guys on the Shiloh forum sicked me onto Jim Kluskens who makes custom inserts.
I ordered two inserts with x-hairs that mike .009". Anything thicker covers too much of the target past 200 m. They arrived and I got exactly what I wanted at $16 each.
He'll make whatever you need or want. Contact him at:
PO Box 138 jim@distantthunderbpcr.com
Niagara, WI
54151