Purchase order change inbound idoc ?

There are lot of threads on Purchase Order change idoc but there's no one explaining the scenrio below.

Scenerio: Client has legacy sytem(E) and S/4 HANA system(S). Now the requirement is to send change PO from E -> S. So from Source system(E) we are able to trigger ORDCHG message type but same message type does not work in target system(S) because it tries to change Sales Order.

Similarly, we tried to explore PORDCHG but this message type is only for inbound and not for outbound.

So do we have any message type which we can use in both source and target systems for PO Change. Otherwise we have to build Z message type(that would have lot of efforts.).

Please suggest.

Thanks,

Vimal