This tray will mount a battery on the headset directly, without a separate Octamount bracket. If you don't need the Octamount to attach a board case or other accessory, this is a simpler option. Variants are available to hold one of 3 sizes of LiPo available from Adafruit:
Small - Fits
1200mAh LiPo (38mm x 59mm x 5mm)
Medium - Fits
2000mAh LiPo (36mm x 60mm x 7mm)
Large - Fits
2500mAh Lipo (51mm x 65mm x 8mm)