I assume that Galaxus also offers the bubbler without gas cylinders. By the way, we have since switched to the cylinders from Linde, which are on sale at Aldi Switzerland for CHF 7.99 (refill). They are 100% compatible and Linde is one of the largest industrial gas manufacturers in Europe, so they are very reputable. For this reason, we currently have a few unused original cylinders lying around empty.