i don't think i've seen anything exactly like that, but as you say it should be pretty easy to modify a pattern--the shape looks simple and b/c it's a wrap it's easier to size. :)
here are some things i came up with:
this is a little different/not as simple, but it has a similar feel imo
maybe this, minus the lacy border and with an i-cord belt instead?
not quite it...less fitted:
you might try rebecca magazine if you haven't already looked there? they tend to have some nice, simple patterns too...sorry this isn't more helpful!
let me know if you do find a pattern that is a good match!