There are several types of sponsorship and endorsement opportunities out there you need to figure out what type of sponsorship would benefit you at this stage in your sport.
A sponsorship is a mutually beneficial relationship between you and the sponsor. This means you both need to profit from the relationship for it to be successful and more to the point, worth it for the sponsor.
Before you ask a sponsor for anything you need to be able to show them how you will have a positive impact on their product or service. How you will increase sales, how you will increase brand recognition of their product, how you will increase their foot print in a new territory or with a new market.
This process will start with YOU. You must build your worth...Be sponsorship worthy...having a logo on your shirt will not be enough..winning a couple of club events will not be enough, winning in and of itself will not be enough..
Have a strategy and educate yourself on the sponsorship process...Some good books are The Sponsorship Seekers Toolkit, and The TASK Sponsorship Guide they weren't too long and they were to the point and easy to read.
best of luck
Tony