Hicks pens can be found with a concealed bulb filler inside the barrel. Unscrew the barrel from the section. Inside, attached to the section, is an internal reservoir with a breather tube and a bulb on the end.
John Holland “Perfection” pens take this a step further by adding a check valve at the junction of the reservoir and the bulb. A small washer will ensure that air flow is directed out the breather tube when the bulb is compressed, but when pressure is released, the suction will pull the washer away from the reservoir, opening accessory air holes, thereby preferentially drawing air from the main channel of the rigid reservoir. The basic idea is similar to the Swan bulb filler with its captive check valve. Pictured here without a bulb to demonstrate the check valve.
