Have a careful read of the regulations.
SCCA GCR states that a fuel cell must be ‘FIA FT3 certified’, this basically means your options are ATL or Fuel Safe.
However CASC regulations state the fuel cell must be manufactured to FIA FT3 regulations or better. Crucially, they do not mention ‘certified’ FT3 containers. This opens up rotary moulded containers such as those made by Jaz, which are much cheaper and less prone to leaking.
Example:
http://www.jegs.com/i/JAZ-Products/547/ ... tId=758786
These cells still need to be contained within 0.060” thick aluminium container, so that cost will have to factored into your costing. So if you do not intend running in the USA, this may be a viable option.