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Yep. Thinnest way to do it, rather than using an actual drawer guide. You could also make them from some stacked sheet stock.

Magnets next to hard drives are not a problem. The falloff distance for a magnet is exponential. And sitting it on the hard drive case wouldn't do anything to it with a magnet of the size you'd use...

Nobody makes them, so you'll probably need to adapt what's available. For something that size, I'd say a push/push type latching system would be the way to go. I think they sell them at IKEA...