Currency on X12 EDI 204 v4010

I need to add a currency designator/qualifier to the 204. I am using version 4010. This field would designate US dollars, Mexican pesos, etc…

I can’t find anywhere on the 204 v4010 standard to do this. I see in later versions (ie 5030) that this is available. I currently have a lot of trading partners using this and converting to a new version could be painful.

Any ideas?

Perhaps as a NTE in the header? The CBH code for NTE01 might be appropriate and then use the ISO 4217 list for NTE02.