I got an email this week that the custom wheel well tanks are back in stock at Curious Campervans. After adding $100 CAD shipping to a US address, this solution is still ~$50 USD cheaper than the Titan Vans product. Noting that Titan might be aware of the competition and has a "sale" price currently of $355 USD (free shipping in USA).
Key differences seem to be:
1) Capacity (22 gal Curious versus 20 gal Titan) and the dimensions of the tanks (how fit around wheel well)
2) No fittings in the Curious tanks, Titan has standard ones pre-installed
3) Titan model comes with some mounting brackets, though not sure what they are exactly