There isn't much out there which really hits your target. Keeping weight under 10 pounds, which I think is a critical factor for travel, and going with ultra short throw widescreen projectors, this is all that I get as results...
If you get rid of the short throw factor, and lower the weight down, and keep things in the LCD world (no rainbows, typically brighter)...
The Epson models that are 'flat' really are designed around portability, and they do keep throw short at about 1.04 at the closest, which is very good for these types of projectors.
They have the brightness, weight, resolution, and size. They aren't as close as you want, but as you said... nothing is that is portable and bright.
The LG laser models are another option, but aren't rated as bright and are a fair bit bulkier, which isn't ideal for travel.
Ultra short throw projection is a headache. It requires a mirror bounce or a very spherical lens system. This tends to be very difficult to work with while getting a very sharp on-screen image and you must have a very flat surface in use for proper results. So, while we are seeing more options available, and a influx of Chinese 4K models appearing, it's just not a part of the portable market because MANY on-the-go presenters don't have any control of their screen. UST is not 'easy' to place when an actual screen is in use. It's one of the most difficult technologies to properly align with a screen exactly. And, the screen must be perfectly flat, which is often not something a portable presenter can control.
I wouldn't expect this to be a hot market anytime soon.