Where should I look? I want a 3.7v hi C and as many mah, you know what I'm looking for..
If you talked to Tom and Danny already, you're going to have to get involved on RC sites and convince someone to produce something for you unless someone has produced something that takes those packs I don't know about.
The high c 1s packs I know about are typically for carpet racers and much larger than you're looking for.
You might luck out with saddle packs if you can find something just a hair over your space constraints and remove the hard case. They're made for vehicles without a single battery bay and wired in series when you install them. Essentially every saddle pack is 2 batteries.
Some of these guys might even have sources for single cells I'm unaware of. That would be great as the technical part is fairly simple as long as you can solder fairly well.
There's always a ton of new crap in RC and battery tech. As far back as both go, amazingly, they can move at the speed of vaping.
Unfortunately, I've settled into my groove so I'm not on the bleeding edge.
But definitely look into (ask about) some of these and info in my prior posts (thoughts come when they do).
Eta; another option is to purchase shrink wrap and 2s packs in the size you want and rewire them as 1s2p packs. It's (again) fairly straight forward.
Tapatyped