From the Adorama YouTube Channel:
Photographing sparklers is great fun and can create a wide variety of images. In this video Gavin Hoey shares his tips for creating simple but beautiful sparkler shots by placing a light bulb in front of the sparkler.
Gavin also shows you how to light the front of the bulb and then dives in to Photoshop for a quick tip on how the merge the two shots together.
This is a great technique to use around 4th of July, Guy Fawkes night, Diwali or new year celebrations but always keep safety in mind. Never touch a lit sparkler and place spent sparklers in water.
Amazon sells antique light bulbs.