Bumping this to see if @Xanthoria tried it and found a good brand. My vet actually suggested it for my old fella who is struggling with chronic pain. He has started to vomit more, which I suspect might be tied to his daily gaba dose 
The CBD is kind of a hail Mary band-aid. Given his previous bloodwork and his bad arthritis, I know his little body is not doing well. When he keeps the Gaba down, he is peaceful, purrs and snoozes almost all day. The vet did give him a 3 day dose of Onsior - and OMG he was his old self on it! Spry, vocal and sassy and wanting to engage with every human he saw. Unfortunately its not for long term use, but it did (in my mind) show that he is certainly living with a degree of daily pain.
Vet and I know that euthanasia is in his future, we are just trying to find ways to keep him comfortable. He uses his kitty ramps and stairs to get to the bed and couch. Mr. BatCoach adores this kitty, so having to make ‘the decision’ might be a hard talk to have with him. Mentally, this kitty is still there, but physically his body is just giving out on him.
Quite frankly, I’m leaning towards euthanasia if the gaba keeps making him vomit. Right now, its the only thing that was giving him relief, but we’ve had 5 days in a row of vomiting it up. Thus, I thought I’d try some CBD as a last ditch effort. This kitty still wants to be here - he’s a fighter, his appetite is voracious as ever, but I struggle with having an animal who is in daily pain.