I haven't tried the Reva flats, but my personal favorites:
1) Keds Champions - the plain old classic canvas sneakers. I think any kind of trainers/running shoes scream "tourist", but these are really clean-lined, and look smart with slim trousers or jeans, and quite "retro" with capri pants.
2) Sam & Libby black leather ballet flats. These are dressy enough to wear with a skirt, and the soft ones hardly take up any room in your luggage.

Naturalizer also makes very comfy flats, and while some models are frumpy, a few are stylish.

I'd also recommend wearing some sort of hosiery, since even very comfortable shoes can rub a bit if you go bare.