Replacement small o-ring
The small o-ring on the front of the handle can be easily replaced. If you need further spares, the specifications for this o-ring are:
1.5mm x 3.5mm ID, Buna-N, Shore A: 70
The o-rings can also be purchased online for as little as US$4.39 per 100 from McMaster-Carr. Search for part number 9262K517.