The panel mount ports, (1 SAE and 1 Co-Ax), are both in a side panel of the bike, not on a pannier or tank bag. I have installed a tank bag bulkhead fitting in the past that is similar, but had a square flat larger on both ends to support it in soft fabric. They are commercially available. LINK & LINK2 (I used link2 on my tank bag)Are you using these on your saddlebags or on a tankbag? Also, if you don't mind me asking, what kind of CPAP battery are you charging? I'm looking for ways to charge mine up in between hotel stops as well.
Your CPAP brand will have a 12v charging system available for it. I use a Transcend mini CPAP and was using their 2 day battery, (P8). But after having two of them die right at the 9 month limit to the warranty, and not fail, but have the electronics die, rendering them useless because they wouldn't charge due to electronic fault, I wasn't going to buy another P8 battery. In the Transcend case, it runs on 19v and tolerates a wide range. I adapted a Makita 18v Lithium battery USB charger kit I had to allow it to power the CPAP. During rides I charge the Makita battery off the bike. WAG, it's a little slower to charge than the Transcend OEM set up with the P8, and I do miss the lack of an indicator light to let me know when it's fully charged, but the Makita battery does have a four bar LED system to check on it's charge. That way I can check it at stops and un-plug it once it's fully charged. My only concern there is just blindly charging it all day may eventually damage the LiFe battery. Of course, it's around $100 for a Makita 3ah battery, Vs the $300 the Transcend P8s were costing.
What CPAP are you using? I have a new 12v charging kit for a Philips Respironics System One that I never used when I had that machine. Different input needs than my Transcend.