From my own search, reviews of the Tripplite B015-000 might work. I'm playing email tag with their sales support and will post the result. The seem confused by my question.
On my own I've tested the:
6KRO - PCPlay PS/2 Keyboard+Mouse Adapter (13ba:0017)
6KRO - Anyware Smart Adaptor EZ-PU21 (0518:0001)
If anyone has different PS/2 to USB adapters, feel free to test using Microsoft's anti-ghosting demo. None of that "quick brown fox" sillyness... We also don't really care about modifiers, so don't say it's 9 key cause you held shift+alt+ctrl+asdfjk. I can do that with the 6KRO adapters listed above. 9 key would be something like asdfhjkl;
Also, of course, make sure the failure is the fault of the USB adapter and not the keyboard. If you can't hold asdfhjkl with the keyboard in a PS/2 port, of course you won't when using the USB adapter!
