Tube air reservoir for a Rapid.
As title. I am a bit fed up with buddy bottles and would like to upgrade my on board air supply to a tube with a reasonable air capacity along with QF and pressure gauge. I use a mixture of regulated and fast flow valves on my Rapids (depending on power requirements) and as the combined QF/gauge/regulator solution is both expensive and involves cutting the stock I don't want to go down that route. Any recommendations?
'It may be that your sole purpose in life is to serve as a warning to others'.