How to store small amounts of gas
A rubber balloon does require some force to get filled. A mylar balloon (typically filled with helium) can be purchased empty (or can be emptied) and requires almost no force to fill; then can be squashed manually to eject the gas. They are available in many sizes.

Rubber balloons also tend to go flat or leak, so their storage utility, especially for low m.w. gases, is short-term (a day or so). Aluminized mylar balloons can hold helium or hydrogen for long periods (weeks and even a month or two). For short-term, you could also use a plain polyethylene sandwich bag - after all, many objects are shipped with bags of air in the boxes to help protect them from damage. Use a needle to insert the gas and retrieve it; tape the area around the needle insertion - like an intravenous operation! Or, you can tape a plastic or glass tube into the bag.

Longer storage would require a gas sampling or collection tube, a glass container with a valve at one or both ends. The internet has many references to these.