If it were me, I would take him to small claims court. If you have proof that he said he would repay the money (email, voicemail or text message), then that's all you need. If you take him to court, he will also have to reimburse you for any court costs if you win a judgement.
If he hasn't sent anything verifying that he owes this debt to you, try to get him to confirm it by sending him an email, text message or voicemail....leave it open ended by saying, "Hey friend, when are you going to be able to pay me back the money for that deductible I lent you? Holidays are coming and I really could use it. If you could just send me a quick note letting me know what's going on, I would REALLY appreciate it".
That way, you have documentation that it was a loan and not a gift. When he replies, then you have total verification.
Please let me know if I can help further.