You can buy a little thing that looks like a cassette tape except it
has a wire sticking out of it with a jack on the end. It goes in the
cassette slot and the jack plugs into the headophone jack of any kind
of player that has a headphone jack. It routes the signal through the
cassette pick up heads. The device works about like you expect it
would work, okay but not great. The main problem with them is the
cassette motor runs when the device is in the player and this may
cause a hum or other interference.

Some stereos have plugs on the back for patching in an accessory
device. I don't know if your Honda does or not. I do think that the
same radio head is used for both Hondas with and without CD players,
so there is probably a set of terminals in the plug that goes into the
back of the radio where you could patch in. You would need a schematic
to find them.

However, both of these require pulling the unit, which you said you
did not want to do. So you may be stuck with the cassette thingey.
They are widely available.

Hope this helps.

Elliot Richmond
Freelance Science Writer and Editor