Need Equivalent Replacement Part for BSI 29C Window Balance

A home owner from Northern VA says:
I'm looking for a replacement channel balance for my single-hung window. What is the equivalent Swisco part(s)?
--ID stamp: BSI 29C
--Window sash weight: 19 lbs.
--Channel width: 1/2 inch
--Channel depth: 10/16
--Channel length (metal only, less end caps): 30 in.
Not sure about the plastic end pieces because their broken.
You were recommended from viewing various YouTubers posting window balance repair and they mentioned you.

Regards,
Ted
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Bob from SWISCO responded:

Hi Ted. Thanks for all the thorough information. We certainly are happy to help. From first glance, this looks like it may be our S380-30 or S385-30. The only difference between these two balances is the 'depth' of the bottom nylon shoe, or the 'heel-to-toe' measurement. The Series 380 bottom nylon shoe has a depth of 1", while the Series 385 bottom nylon shoe is 1-3/32" deep.  See which most closely matches your old hardware. If the dimension happens to be less than 1", then you may need a custom balance; just let us know. In any event, you will need a stamp option of 2930. 

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