It will be expensive, but is partially possible
We don't stock extra parts for resale in these categories because our minimum order quantity is 100 on these parts.
I built the prototype Quest V2.0 on a V1.0 frame with parts I purchased at retail. I learned a few things.
1. The retail version of the DualDrive hub is a 36 hole hub. The OEM version we use on the Quest is a 32 hole hub. As I remember, the Sofrider rim is also 32 hole. You'll need a new rim.
2. The cost of the hub kit (including shifter, hub, clickbox and a few installation parts) was $473 US from ProWheelBuilder.com (but they no longer sell it, last I checked). The cost to have the LBS source a rim closely resembling the Quest 26" rear wheel, and build the wheel, was $140 US. (I'm not a wheelbuilder).
3. You can use V-brakes on the wheel if you buy the appropriate rim, with braking surfaces. The hub comes with a cover for the disc mounting holes on the hub.
4. We have considered offering e-ring packages as aftermarket parts (John is the patent holder) but our capital is tightly tied to the overall business plan, which is currently centered on development of new bikes and supporting competition. Bespoke aftermarket parts aren't near the front burner for now. You would need to use a commercially-available eccentric chainring.
I suspect all this wasn't what you were hoping to hear, but I hope the information is helpful.
Best,
Doug