Thanks for all of the suggestions!

The Wingnut looks very interesting, but living in Canada it would cost too much by the time I added in shipping, duty, taxes etc.

I have thought about the bottles behind the seat, and I 'think' it would work. We ride mainly double track, forest service roads and any steep downhills we get off the bike. We prefer riding uphill to downhill. I like the look of the Profile RM System Jesvetmed suggested. Our rides are usually 2-6 hours depending on the day of the week. The longer rides I would have to carry more than 2 bottles for sure if the weather is hot.

This forum is great! Thanks again for all of your suggestions.