I have been searching for the RCA 800 but unfortunately it does not appear to be available online at all and when I contacted Sennheiser US, they knew nothing of it. I've ordered a cable from double helix that'll serve as my iphone/android cable. It's expensive, yes, but I've had Peter custom build me a cable that'll work with both my SE846's and IE800's by making the lower portion of the cable removable with a 2.5mm connection point. This way I can make dual use out of the cable for both my IEM's. I'm still a few weeks away from receiving it so when I do I'll post some pics of the setup if anyone's interested.
The only downside to the new remote/mic that Peter offers is that it's not MFI certified, meaning that there are no volume up/down buttons. It's a bummer for me that it won't have the volume buttons but hey it's better than nothing! Hopefully in the future Peter will be able to secure some MFI certified remotes that I'll be able to upgrade with.