Coming up with the down payment proving difficult

I am wanting to become a new franchisee but in an established area. Judging from my screen name, you know in what service industry. The sale of the business is $305,000 but after franchise fees, closing costs, etc. we are looking at a total project cost of around $342,000. I am looking at getting an SBA loan and after having discussions with the bank, it has been determined that the best way to go is that we put 20% down, the seller does a 10% seller hold-back which I would pay over 5 years plus interest, then have the rest be financed. The plan actually sounds good to me other than one thing, the 20% is proving elusive. My question is this... Can I get a private investor that can serve as a lender to give me that 20% down without giving them equity but rather treating them as a lender? Or would that be looked upon as me incurring more debt and it would not count as assets? Is there a way around that? We have worked tirelessly on getting this business and we HAVE to find a way to do this. Please help as my family's financial future is depending on this working out.