If you have the LED version of the Strion, try the STRLD-1 or the SFRLED holder.
Unique open top holder for the Streamlight Strion utilizes a closed-cell foam "pillow" sewn on the inside of this holder to allow for positive retention but easy access to light. Holder can be shook upside down and light will remain in position. Utilizes only best quality, Top Grain US leather and heavy duty nylon thread.