MFJ does make a box which allows the ATAS to be operated manually, but that's as close as you can get.
The reason is, the ATAS uses the applied voltage via the coax cable to determine which direction to move the antenna. No other radios does this, except those made by Yaesu.
You be much better off replacing the antenna with a decent HF screwdriver or HiQ, and a Larsen NMO2/70BK. In fact, the difference is so astounding, you'll wonder why you ever put up with the ATAS.