Greetings! The Trap's designer here - US screws are - screwy - ahem. Smaller sizes go by a whole number so #4 x 3/16 is a number 4 screw diameter 3/16" long. Once they get big enough in diameter they go by fractions - I know - silly. Many times there is pretty close approximates in metric. Metric screws are typically listed as M2 x 10 for example - 2mm diameter x 10mm length. If sourcing locally I would recommend Googling a US - metric conversion chart and getting closest equivalent. The amount of hardware needed is tough to round up even here which is why I started offering hardware kits, check them out if interested.
That looks perfect, I'd probably easily spent that much on screw, not even including the time figuring out the local conversions and driving around finding them. Plus I'm happy to give back somehow for all the time you've spent designing the kit. I just placed my order. (Order #1249973511)
I'd love to get the Deluxe hardware kit but can't really justify spending that much unfortunately.
Off topic, I noticed your giant LEGO classic space computer, I'm a bit of a LEGO nut myself (Created the LEGO Ghostbusters Ideas set, worked on the LEGO Batman movie), I do custom minifigs and recently did some electroplated chromed classic spacemen (http://www.wallercustoms.com/
If you're interested in any of those perhaps we could arrange a trade for a deluxe hardware kit? If not, no worries, I've put in my order for the screws and plan to spend my weekend prepping and priming my