Portland Design Works (PDW) have blogged on their new saddle bag rack, the
Brindle. Apparently the first batch was sold out but. They had it listed for US$88.00 and it weighs 13 oz (350 grams).
From the blog:
The Bindle™ Rack’s design includes a lightweight alloy platform and heavy-duty compression straps that loop through saddle rails to securely hold gear or stuff sack. The rack mount fits seat posts 22.0-31.6mm and installs in seconds using a 5mm Allen key. The Bindle™ is rated to carry up to 5.4 kgs (12 lbs). The design eliminates the potential for side-to-side sway while riding and rear wheel rub for riders with short seat posts.Another option and relatively low cost.