Try a local lender.
It's not uncommon....It depends on whether the buyer can afford to pay the difference and if the type of financing they're using allows them to. If the financing is a VA loan, then the buyer is not allowed to pay any difference. The buyer needs to decide if they want to pay the difference in cash - do they want the house enough to pay the difference? Another option might be to meet half way - if the seller will agree to that.