why not make your own?

http://www.craftstylish.com/item/43227/how-to-make-a-reusable-sandwich-wrap

or

http://craftgawker.com/post/2009/06/17/1567/

There are sandwich sized tupperware containers that I use. Something like this one from the Container Store, but I got a 4 pack from Harris Teeter for something like $3.

I just wash out the ziplocks. They last a surprisingly long time!

www.eekowrap.com

This keeps your lunch fresh and doubles as a placemat. It's awesome and saves lots of plastic bags.

There are literally a million of these in every size and pattern you can think of for sale on Etsy. Type in reusable bag and you'll come up with more than you can shake a stick at.

Love the craftorials! When you've washed and reused you last ziploc, why not use wax paper and a rubber band? You can re-use it and when it's worn out you can throw it away knowing that it's biodegradable. Extra points if you use soy wax paper or paper with recycled content.

I think mine came from Crate and Barrel [could be wrong might have been Container Store] very heavy nylon with velcro closure. Washable, tough has lasted for years.

I love the reusable bags from Snack Taxi: http://www.snacktaxi.com/

The prints are so cute I'm always excited to use them, and mine have stood up well to both machine and hand washing. I carry my breakfast in one almost every day!

Reusablebags.com has a huge selection of sandwich bags. I've bought a bunch of stuff from them before and I'll swear by their customer service. Fast and efficient shipping, no hassle at all.

I really like this sandwich wrap from Abeego. It's nice cause it's flexible; it can handle sandwiches, pizza, baby carrots, anything non-liquid really and it takes up very little space when it's empty.

http://www.etsy.com/shop/obleek

a friend makes them - and a bunch of other cool stuff

My husband & I started using the Bag-E-Wash in our dishwasher to wash and reuse Ziploc bags, and have been very pleased with the results...

http://www.bag-e-wash.com/

http://www.etsy.com/shop/lolabags?section_id=6507339

There are so many to be found on etsy!

I have a sleek, black, monogrammed lunch tote from LLBean. I've had it for years. It's bigger than I need, so I don't run into space problems if I want to bring something bulkier. I use one of those contained ice block things that freeze and it keeps well until I have my lunch a 1:30p. It isn't supposed to be machine washed, but it washes beautifully.

I use the bags by Kids Konserve (they come in perfectly grownup-looking designs). They seal with Velcro and rinse off in the sink.
http://store.kidskonserve.com/Food-Kozy-p/kk052.htm

I can definitely vouch for the Abeego wraps - they are fantastic! And they smell wonderful, just slightly of beeswax.

I have a bento box specifically for sandwiches, and it is really awesome. No smashed sandwich! The sides fold down, and the whole base fits into the lid so it doesn't take up much room when empty. Still plastic, but definitely reusable.

I have tried different kinds but my family really likes Greentime Bags the best http://www.greentimebags.com/
We love them! Our sandwiches and food doesn't dry out as fast as it did in other bags I have tried. I can leave chips in them for a couple of days and they are still fresh. We feel so much better using reusable sandwich bags than ziploc.

..! lunch skins, hands down: http://www.lunchskins.com/home.php?cat=

@kakugori Where can I find that? Is it BPA free?

@libbet have you tried theme yet? I am also looking for a better alternative to wrapping my sadwich in foil and rinsing and recycling the foil.

@crogers Can I have a sloppy sandwich in these bags? Veggie burgers, tlt's, etc

I like the snack bag idea for snacks, ie. almonds, granola, grapes, even a sliced apple. But I am concerned about a leaky sandwich.

I've purchased most of my bento boxes on ebay, but there are a number of online shops that sell them now. If you have a large Asian market near you, they may have them as well.

As for what it's made of, well, I honestly couldn't tell you. If you are concerned, probably best to ask the seller before buying.

That said, the only thing that makes my sandwich case special are the folding, vented sides. (Well, and it's cute.) You could use a similar container you already own that meets your needs.