my advice, find a junk yard somewhere near you and look for a 99-00 civic si that has been absolutely totaled. The single plug you need to re-wire your harness should still be intact. Most places will try to make you buy the entire harness, so dont tell them exactly what you're lookin for, just tell em what kinda car. Buy a little something or other off the car from the interior and just snip that plug off
even if he gets that plug he'll need to rewire more than that, the wiring setup is different and all the wires on the center plus are not the ame just in different position. They are kinda scattered in whats been changed.
right, he needs to use his dx harness, get a jumper harness to go from obd2.a to obd2.b, and run the other wires needed, i think that is your best route out. or do what i did, and get a p28, go back to obd1, and use an obd2 -> obd1 jumper harness.. obd1's are easier to tune.