It can be done with AHKHID, however, it is not completely straightforward.
Essentially, you set up a hotkey as normal, then use AHKHID to detect which keyboard sent the input. Based on that, you either send the original key (equivalent to not remapping), or send the remapped key, depending on which keyboard it is.
However, AHKHID is considerably more complex than basic keyboard remapping, and I can't find any examples to demonstrate what I'm talking about.
As an alternative, you could use LuaMacros, which natively supports multiple keyboards, although is not as full featured as AHK. For a simple remapping, it should probably suffice though.