You're highly unlikely to find it posting on forums. Sponsorship is a tough sell from Nascar on down and probably harder at the local level. Convincing the sponsor that his name on the side of your car is going to bring him more than he gives you is very hard because usually it ain't going to, or if it does he can't measure it. I'd say most local sponsors do so because they just like racing or the racer.
Think hard about who might get some benefit from advertising on your car and then knock on their door(you gotta figure out who controls the money too). For example, any business near or on the way to and from the track(restaurant/bar,c-store,etc.)that gain customers from race track spectators. Be creative;for example, offer to advertise a weekend race special price on the car, or whatever. Offer to display the car at their location, or hand out their coupons or paper ads, etc. Remember you,your crew,and your eqpt. represent the sponsor so appearance and conduct must be first rate. You know, no K.&K. Busch. You will find many sponsors prefer to give you merchandise or services rather than cash(food for crew,gas for truck, parts, whatever). Number one thing to keep in mind:what can you do for them,not what can they do for you. I once got sponsorship from a major automotive paint manufacturer by doing a presentation that showed high exposure to bodyshop operators in a regional touring series, and agreeing to approach these potential customers with some low-key sales materials & vouchers for samples.
Good luck with your search.