29 3 B.S.I 0L Channel balance

This looks like either an S380-30 or S385-30, depending on the bottom nylon shoe depth, or 'heel-to-toe' measurement. Compare both balances with your old hardware to see which matches best. In either event, you'll need a stamp option of 2930.

Comparison of the S380 and S385 balance shoes.

Thanks for replying. Yes, the depth does look closer to the Series 380 to my eyes, but double-check to confirm. If it's any less than 1", let me know. 

Some of our suppliers have been working with limited crews this summer, so unfortunately some of our balances have been out-of-stock. They've been consistently coming back into supply however, so I don't think it will be much longer for the S380-30 to return either. Apologies for any inconvenience.