everybody uses liquid co2,,, you couldnt store enough to last for very long otherwise,,
i suggest buying the ecotechnics regulator,,
http://www.growell.co.uk/unis-co2-controller.html#tabs
you can buy 10 kg refills at many hydro stores or you can get much bigger bottles from specialist gas merchants,, id advise just going with the small bottles though as it weighs a ton,,
i dont understand why a company would state gas only rather than liquid because all you need to do is exert less pressure on the liquid for it to turn into a gas which is what regulators do,,,
LOL mann were all wasted. Lost in sea it states that mate on your link.e.g " Use only with vapour release CO2. Not suitable for use with liquid C02"