You need to be able to show them a potential return on their investment. Sponsor's give money, not as a donation, but as an investment. Yes, some businesses sponsor youth sports and the like and do consider it a donation. I have done it for years and have yet to get my first customer from it. 100% loss in terms of money. But it is for a good cause in my opinion. Youare looking for $$$ to start a for profit haunt. Whats in it for them.
All that being said, try local hardware stores, ones you plan to purchase materials from. Local food / pizza places. Try to get a promotion developed that offers cupons to both places. Buy a pizza, get $5 off admission. Buy admission, get $5 off a pizza. Make sure you have hanouts to pass to your customers as tney leave that includes a VERY short thank you letter to any and all sponsers. Also include the associated cupons. Good luck.
The secret to getting sponsors is to realize that sponsorships are really and advertising/public relations scheme.
You have to offer them some advertising for the money you're seeking. For me, success came in the form of perverting athletic field sponsorships - I'm using 3x3 yard signs (the bottom end size-wise to the sponsor signs they hang on little league fields) as part of the crowd control barrier system. Everyone who has been to an amusement park knows full well how boring it is to stand in line and you will read every last sign you see repeatedly. It also helps in your first year to plan on using those signs for several years.