Rear Rack With Seatpost Attachment

This rear carrier from Ventura has some features not formally found in an economy carrier.  First, it will attach directly to your seat post with 4 allen head screws.  Second, the loading surface can be shifted forward or backward to accommodate what you may be carrying.  It even has attachment points for your bungee cords!  Will carry a maximum load of 10 kg (22 lbs).
This carrier uses 4 screws to attach to your seatpost
For seatposts with diameter 25-31.8 mm
Has attachment points for bungee cords
Loading surface can be shifted fore and aft; surface area of 33 x 12 cm (13 x 4.7 in)
Can be loaded up to 10 kg (22 lb)