Yes, you are correct that finance contracts with an APR of greater than 12.5 percent (12.5%) are not normally eligible for gap coverage since GAP insurance providers cap the APR rate at this amount. 

Restrictions to a full Gap policy typically include:

• Maximum Limit of Loss: $50,000
• The claim settlement may not cover the entire Gap due, when your loan's Original Amount Financed exceeds 120% of MSRP (new vehicle) or NADA Retail Value (used vehicles), plus 30% of Value allowable for Additional Financed Items like Credit Life or Service Contracts. The claim settlement does not cover late charges or other penalties due to your lender.
• Your loan amount financed must be less than or equal to $100,000.
• Your loan term must not be greater than 84 months.
• The loan must not have a balloon payment due at the end of the term.
• The maximum APR is 12.5%

Notable general GAP exclusions include (meaning gap will not pay out for these items):

• Overdue lease/loan payments
• Financial penalties imposed under a lease for excessive use
• Security deposits not refunded by the lessor
• Costs for extended warranties, credit life insurance, or other insurance purchased with the loan or lease
• Amounts deducted by the primary insurer for wear and tear, prior damage, towing, and storage
• Carry-over balances from previous loans or leases
• Equipment added to the car by the buyer, meaning that only factory-installed equipment is covered

Full gap insurers are different than insurance companies that offer Loan/Lease GAP coverage (known as LLG or Gap). For example LLG coverage with Progressive on a Florida policy notes that this coverage:

• Is available if there is a leaseholder or lien holder on the vehicle. A lessor or lien holder can only be a financial institution, it cannot be a private individual.
• Provides coverage when a vehicle sustains a total loss.
• Covers the difference between the actual cash value of the vehicle at the time of loss and the amount owing on the loan or lease. (Payment will not exceed 25 percent of the actual cash value of the vehicle at the time of loss.)
• Can be purchased on new and used vehicles at any time during the policy period.
• Collision and Comprehensive coverages required.
• Payment will not include unpaid finance, excess mileage or any other charges or expenses associated with the loan or lease.

So while a full gap insurance coverage may not be available to you if the APR on your financing agreement for your vehicle is over 12.5% you may be able to get LLG coverage that doesn't have an APR exclusion, the policy contract will define if there is an exclusion.

Loan/Lease Payoff coverage is slightly different from Gap insurance because a maximum payout of 25 percent of your vehicle's ACV is stipulated in your policy instead of full GAP insurance which should pay the difference between what is owed and what the Physical Damage Insurance Company pays out (the ACV of the vehicle). Still if you are not able to obtain gap insurance but can get LLG coverage than it may be worth it if you have negative equity in your vehicle meaning you owe more than the worth of your car.

On our site we display either a Gap insurance or loan/lease payoff coverage option for Esurance, Progressive, Hartford, Travelers, Safeco, and Unitrin Direct in most states, along with Customized Parts Coverage. So you can see if any of these meet your needs however they require you to purchase your primary auto insurance coverages with them as well.