Coil balance spring replacement

Hi. I have several windows in the house that have broken coil springs. The company that installed these windows call windows of the world are no longer in business. Can you help me find the correct replacement ?

Hi again! Thank you for your help. So I need both left and right side. The sash is 12.6 lbs. Do I order:
2 x 15-140
2 x 15-150 (6 lbs or 7?)
2 x 15-143
2 x 15-144

If you can confirm or clarify the above, I'll start placing orders. I have up to a dozen windows that need similar repairs.
Please let me know. Thank you very much!!
Bob

HI, Your team has been great answering my questions and even editting an order for me that had an error. I've placed 2 orders and repaired 8 windows without a problem. Excellent. Your series S150 Coil Balance only goes up to 7 or 8 pounds per single spring per side. I have one more window to repair but this window weighs 23 pounds. Can you help me find the right set-up?

For the 8 windows I've already repaired, I used the 15-140 coil balance shoe with 15-143, 144, and 145 parts along with the series 150 coil balance.

Thank you! Bob