loaning someone some money
This sounds like a cash loan to an individual. Nobody is going to insure this - it would be too easy to run a scam. For instance, you could "loan your friend" $100,000, and take out a policy for a $10,000 premium. Then your friend "doesn't pay you back and disappears", and the insurer pays you $100,000. You've just scammed the insurer for $90,000.
If you're going to "loan someone some money" and you have doubts about whether they'll pay you back, your best bet is to get collateral, and be ready to lawyer up if needed. I prefer to leave lending like that to the professionals, aka banks.
Rob and Kenneth Vogt mentioned factoring. That doesn't apply to cash loans, or loans from or to individuals. It purely applies to business-to-business sales, and it's not really a form of insurance. Instead, you sell some or all of your receivables to the "factor" at less than the face value. In determining how much less than the face value you'll get, the factor will take into account your creditworthiness, the other party's creditworthiness, the size of the transactions, and the other party's payment history to you. They may simply decline to buy receivables that are too sketchy, in which case you'll be stuck with them.