cilogear although not front loading
i think mammut might have a front loader
you should ask under a rock climbing forum

they all have top loading, the question is if they have good front access. The REI Mars opens up like a suitcase, it has the best access I've ever seen, but it's a little cheap and isn't really pro quality (I owned one and, though I really liked some of the features, I returned it). I have a Gregory Palisade that has good front access, but you have to go thru the front pocket to get in there - the zipper is inside the front pocket. Many other packs have at least a zipper in the front somewhere for decent access, but actual "loading" options are few and far between. You're probably gonna have to settle for front access rather than front loading.

Now, front pockets for extra storage, climbing gear, etc . . . , there are packs that are specialized for having certain gear in the front for quick access (like the Palisade), and some are made specifically for climbing and mountaineering and skiing etc.... I'd start by looking at Gregory and Osprey and Arcteryx, as they've got those kinds of options and specialties all worked out. There are other brands, but they have good selections.