Yep, that is mostly what I did, only the person in the video spent more time trimming and gluing up parts. The extra time obviously made for a nicer looking end product.
How much is your time worth? Mine isn't anywhere near $249 per hour.
My junky little optical viewfinder does a good job and my cost was an hour of my time, a single use camera, a little decent quality electric tape and a small Velcro patch.
For those with no mechanical skill and/or no patience for crafts, with the way every camera manufacturer is releasing this style camera, I expect you'll find some enterprising Chinese plastic injection molding shop will be selling these out of Hong Kong for $9.95 on eBay before you know it.