Finding the right mentor depends on what sort of support you’re seeking. If you’re new to your club and want someone to help you settle in and find your feet, you might benefit from having a buddy - another volunteer who knows your club well. If this is the case you could talk to whoever looks after the volunteers in your club to find out if they have a buddy system. If not, they may still be able to suggest someone who could help you.
If you would like mentoring in order to help you develop in your role, then you really need someone who is more experienced at what you do than you are. Sometimes it will be possible to find this within your club: for example a qualified coach could mentor someone who is just starting to study for a coaching qualification. Sometimes, however, it might be that the right support for you is outside your club. If you have a management role such as chair or treasurer you might benefit from talking to people outside of your club. Perhaps someone who did your role previously could help, or someone who does an equivalent role in another club near you. For people in club management positions, the Club Matters mentoring scheme can also help.