Audio research may be a touch slow to respond, but they will. I have had excellent service from them on several occasions. Try reaching Kalvin Dahl Via the voice directory on the phone.
Ask if they used the same IR code as the CD-3/5/7/8/9.
The CD-1 was also Philips drive based, so it should have been using the very same RC-5 protocol.
In any case, you can get one from ebay - the cheapest I found is $10 shipped.
Look for 'Remote Control For Marantz C4001P RC63CDl CD85 CD50 CD63KIS RC67CD CD Player'.