I was referring to bottled gas from a supplier. Here in the UK you can get a bottle of compressed hydrogen for about (from memory) £75 but you have to buy your own regulators which are around £150 and the bottle is only leased to you for £15 a month and you don’t get any refund for unused gas when you hand it back.
There have been a few trials with people making their own but getting it pure enough seems to be the challenge, specifically removing all the water vapour which gas produced by electrolysis contains. The need to remove any water vapour is because the balloon will experience very low temperatures, - 60C is possible and any water will turn to ice. There’s also the minor issue of safety producing hydrogen in volume at home. 
However, a pico balloon (as they are called) like this one doesn’t need a lot of gas so it might be worth thinking about.