You can buy a gallon of LPS-3 on Zorro.com for $62.59, with free shipping.
You can buy a gallon of Fluid Film for $42.59 at Advance Auto parts.
I use both products. I have a 16 gal. drum of LPS-3
LPS-3 has a Mil.Spec for corrosion protection. I do not believe that Fluid Film has a Mil.Spec.
LPS-3 will last through several hundred hours of direct water abrasion, before needing to be reapplied.
In past years I have rustproofed the panel interiors of all my cars with LPS-3.
Fluid Film is prettier, because it is clear.
LPS-3 is brownish, but is much longer lasting.
LPS-3 has been used in commercial aircraft cargo holds for years, as corrosion protection.
LPS-3 is not widely known in the homeowner/consumer market, but in my opinion, it is a superior product.