Metal or plastic box? I've also made a post about the SX350 I ordered but nobody has replied in days. Do a quick search on here for SX350 and dig up the other user's stuff, that's what I did. I had already gone out and purchased some acrylic panels because I couldn't find the "perfect" shaped box pre-made. I think if you want a perfect size for your chip, you'll have to make it yourself. Another poster on here did a really really excellent one out of acryllic and shared how he rigged up the button/switch.
As for the 510, most users just wire one themselves. I'm going to (attempt) to use a flat-top Chi You conversion for my 510. I'm hoping to use a mini turnbuckle-style get up in mine to let it have an adjustable center pin... we'll see how that goes. Was also thinking the center pin with a male Y-clip sandwiched onto it so that the wire doesn't have to be stressed when the pin is rotated. Anyway I like the idea of a nice solid metal base on top of my plastic box, with a really sturdy steel 510.
Making the cut for plastic is simple enough.. 1) use clear plastic for the window and no cuts have to be made for it. 2) if the plastic is thin enough, just measure, trace, and cut it short with a soldering pen and then sand down the edges so it looks nice and neat.