I'll be posting the bulk of suggestion for the bottoms as pants...it's obvious if you're trying to achieve the same look as the guy in the picture that his pants have been rolled up to achieve that tightened look around the knee area. I posted 2 examples of camouflage shorts for you, but they don't look anything close to what the guy in the picture is wearing. Besides, if you look at the other pictures of what he's wearing on the blog, they are actually pants and not shorts (:
Also note that the rolled up look would look neater/better if you're wearing slim/straight pants instead of flared/bootcut ones...and once again I didn't check etsy or ebay, but the guy mentioned on his website/blog thing that his pants were thrifted for 12bucks only, and they look pretty amazing to me, so I think you should try hunting round in those 2 websites since they have a larger variety of vintage/secondhand goods for much cheaper prices than regular retailing items (:
I'm pretty sure you can find plenty of denim vests online, but I'm not very sure about US shopping websites. From the image source, he mentioned that his denim jacket was vintage, so your best bet would be to head to ebay or etsy and try your luck there.