Zappos best pick for flat feet?

I just finished my 3rd day doing stow and my feet are causing me a huge problem. I have flat feet which make running/walking/standing painful after awhile, never have been in this much pain during a 10 hour shift before. It's causing me to make mistakes and going for restroom breaks just to get off my feet for a bit when the pain is too much to handle. I worked at a dsp and a DS before and neither of those was this bad. I'm a big guy, almost 300 lbs, working for the dsp just made me tired and stiff with not much pain, the DS was painful but not to this degree. Walking around kind of eases the pain but standing still at my stow station is killing me, even with the floor mat.

My question is if anyone had any recommendations for a zappos shoe/insole and if anyone else has come across this issue. I was referred to the wellness center but I'd rather just get the right footwear for optimal support. Not trying to end up needing extra breaks everyday.