Photographing beer - how to diffuse single flash for photos of glass and bottles?

One of my hobbies is beer. Rather informally before I drink a new brew I like to pour a glass and take a few shots. I don't want to use anything like a light tent or anything more than a single flash. Right now I am using an old manual flash a Sunpak Super 383 with a Gary Fong Lightsphere bot hand held with the flash held above the camera. Overall the shots are good enough for my purposes but was wondering if there is a better flash option that could still be hand held, I am getting some harsh reflections especially on foil labels. I do have a little slave flash I could also use in addition.

Examples.

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Oll an gwella,
Jim