Can anyone suggest a decent handlebar bag for use with trekking handlebars? Specifically, I have an REI Novara Safari. I'd like a bag which has a see-through map case on top, but which also is easily detachable to carry along with you (i.e. has a clip, not velcro). I've looked at many, but they look like they may have issues with the bar configuration on trekking bars. Ideas?

Phil