Bag for backpacking with m4/3 gear

I am heading to Philmont with my son next summer and we will be starting our preparations with a series of 10-15 mile hikes with a full backpack.

For these hikes, as well as our actual trip, I will be bringing my E-PL1 w/kit lens and probably my 4/3 9-18 and 40-150. I may swap these out for the m4/3 equivalents prior to our trip since every ounce counts. Am also considering the 7-14 instead since there will be many great photo opportunities.

Anyway, I am looking for suggestions on the best way to carry my gear - a photo backpack is not an option since I will be wearing a real backpack - and I want to have easy access to my camera.

Thanks in advance.

-Jeff