One way is as in the diagram. The pump is modified with 2 washers, one face upwards - this makes the pump suck as well as blow.A valve with 2 one way valve is required to direct the gas flow into the pump and then into the vessel. In my case they are ball valves easily made from brass tubing and a couple of ball bearings.I have filled balloons with Hydrogen with a similar set up. Your not going to develop much pressure though.
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A bike pump may not be the best approach. You need to seal the inlet valve to your gas source, and the outlet to your tank.