I got this one:
http://www.dirt-bike-gear.com/lfb.html
It's a bit of a love hate relationship. It holds all the tools we need on the trail, but it can also be in the way when riding technical stuff, if I want to slide back on the bike, the bag is in the way. Its not enough of a problem yet to get rid of it. I'm 6' and its on a 250, so no issues with kicking my leg over when getting on / off the bike.
The alternative is a similar size bag on the front handlebars, I'm not a fan of that given the extra weight you'd constantly be turning. You also have the good old fanny pack, back style, which I personally don't like, extra weight on me is a non starter.
I've had several outings in boogie so far this year with it, no regrets, it works great and I don't think I'll change setup.
I got it directly from the maker on the site I linked, but you can also order it from gnarley parts if your not a US shopper.