Just looked at a picture of an '07 and looks to me like there should be plenty of room to put a bag on one without blocking the vents. Unconventional sources might be soft sided tool bags/pouches found at Home Depot, Lowe's, hrdwr stores, etc. There are actually some good looking ones. Or say small soft sided pet carriers. That's what's on my Xciting.
If there's any metal underneath the floorboard, you might could use magnets to hold it in place.
