Does anyone have a women's Trek Verve or similar hybrid, 18" or larger, with a rack, that they aren't using right now?

The frame cracked on my bike. It's under warranty, but apparently could take a couple of weeks to repair. The bike shop offered to give me half off on a rental bike for that period. However, the biggest women's bike they have is what I think is a 15". I'm 5'9", and the one I usually ride is a 21". After just one day, riding only about three miles, my back is killing me. My normal commute is 12.5 miles, and I'm not at all sure I can handle that for two weeks with this bike.

I'd be happy to pay someone else the $45 a week I'm paying the bike shop, if I can get a bike I can actually ride. If anyone has one, or a lead on one, please let me know!