Hello there!
Thank you for reaching out to us. We can help supply this balance but it will have to be a custom order due to its configuration. The pulley wheel is built into the bottom fitting itself and this balance features an extended cord travel as well as a metal channel length ending in 5/8" which is what makes it custom. For example, the metal channel should measure 20-5/8" long. Can you double-check that for us? We can't promise our replacements will work for you if the metal channel length differs and custom orders are nonrefundable so we'd like to be sure.
The term "custom order" doesn't mean that the part itself is unique, it just means that it's not a part that's commonly available in our catalog and so we have to acquire it by special means. To put it another way, the part isn't custom, but the order is.
Unfortunately, a stock balance can't replace what you have here. The issue when trying to use a stock balance to replace this is that if you were to use a 20" version, both the metal channel and cord would be too short and the sash wouldn't be able to close. Meanwhile, a 21" would be too long, and you'd run into the same issue.
With that said, I'm going to email you a purchase link and price quote for (2) of these balances for your review. Let me know if you have any questions!
