It's a different sport then mine but even small sponsorships help. You need to market yourself. A letter showing your accomplishments, what social media you have (I have about 8,000) on Facebook an (4,000) twitter. It's not alot compared to some but helps when asking for things. Sponsors will view you as a marketing resource an how many people you can drive to them. Say an event in 3 months in Vegas, you can let them know the attendance (30,000) it would reach. Also what type of package you are asking for an where the money would be going helps.
I had a local farmers insurance sponsor me once on $1000 a month for 3 months preceding the event. Remember it's a contract an even included 10 posts per week online (automate it with hoot suite) they got 4 event tickets, a section on the banner, an on a t-shirt. Their money in their eyes went to offset food an training costs monthly.
Think outside the box an who you know that can contact. Someone who knows someone can help. Small business an money helps an will add up. If your going for local shows go to local business networking events an look for people interested.
Currently I have a tshirt company (something I would never wear) offering $300 a month plus a ton of tshirts, a internet marketing company offering $300 a month, and working on a few others. Even tho these companies havent done much in the industry and the extra money helps while trying to get out there more. If you need a link on a sample letter let me know!