Need legal advice and/or sample for agreement

I am helping a new startup with strategic marketing and pr, creating the branding and logo, website and copy writing and bus strategy. these are 2 new bus owners, they do not want me to come on as partner. But, i have figured out a creative way to do profit sharing. I would like to get a Fee for each "widget" sold. widgets are already selling, due to initial efforts. I have startup experience so i am advising on many levels as well. i can not afford an attorney so creating an agreement myself. any ideas or a sample that could help with this? i have researched equity agreements and independent contractor agreements but neither works for me to cut and paste something together. this is an initial agreement. i do have a small business legal adviser to look over the final before signing, but that is all i can do. so sample agreement of this type anyone? advice?...thank you