A bit of an update: There was a phone number on the package Dominic sent me, so I called it. Sunday afternoon I spoke with a nice lady who I can only assume is his mother. She assured me that she would have him call me back to sort the situation out. Apparently he doesn't listen to his mother as I've not heard back. I tried calling today and got the answering machine, so I left a message. I'll not be holding my breath.
I feel as though I'm being enormously patient through this and have shown good faith, yet I've gotten absolutely nothing from him. If I don't hear back from him tomorrow, I'll have to file a PayPal dispute as I have no choice but to conclude that he's willing to keep my money without delivering a functioning product. Sad, really.
A bit more of an update: As I didn't have time to wait for Dominic's non-answers, I ordered an ORP/Flex combo from CFM. Easy checkout, prompt shipping, included hardware and an absolutely perfect fit. Lesson learned.