I'm in lurrrve with lots of good stuff at babyearth.com, but am hesitant to register with a website as I have to pay for any returns, which can be a hassle. It's amazing what they've come up with in the past 30 years (since I was a baby). One of my favorite items that I've seen both online and in person at friends' baby showers is the Cloud b Sleep Sheep.
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This is their "on-the-go" model, which is made smaller for travel, which I will probably do more of in theory than reality, but still. It has four soothing nature sounds and a sleep timer so you can set it to go off in either 23 or 45 minutes from when you put your little one to bed. Hopefully, that will be enough time to get him to sleep! If this doesn't work, I'll have to resort to singing to him... and nobody wants that.
$21.95, babyearth.com.