Vitronox makes magnetic knife sleeves that work really well. My cousin is a chef, and uses them for both storing and transporting her good cutlery. Just lay the blade on one side of the cover, and flip the other side over. Since they are magnetic, they literally snap right on, and won't come off until you want them to. Much better than the plastic ones you're looking at. Most kitchen stores should have them, as well as Amazon.
Of course, if you're even remotely handy, you could just go and buy some of the flexible magnetic material (like they use for car signage), and make them yourself.
For camping, we just bought a semi-decent set of knives from a kitchen store (think they are Caphalon) that came with their own plastic sheaths. Since we're in a travel trailer, they just go in one of the drawers under the sink. But for car camping, any knife or tool roll will work - or buy some heavy canvas, leather, etc., and make your own - scrap material at a craft/fabric store can be had for next to nothing. (I'm cheap, and like making my own stuff when I can).
Someone else mentioned a cutting board, and if you don't already have one, they are indispensable. Normally, at home, I prefer wood, but for camping, I keep a small plastic one that's roughly 8x12. They're cheap enough that when one gets too beat up, I can just replace it. And since it's plastic, I don't worry about it getting left in the rain, or otherwise abused.
If you really want an all-in-one setup, checkout the Gerber Frescape set. Top of the box that acts as a cutting board, and the two knives fit in their own slots inside the box. I have no idea on the quality of it, but for car camping, it looks like a nice little set-up. Should be able to find them for $25-$30 all day long.
