Bicycle Source US finally got back to me (with a "did you not receive my first email?" query ). They offered to let me keep the wrong rack for 23 bucks and to send me the correct rack right away. Since it's a $40 rack I decided to take them up on their offer, so all together it's gonna cost me about $68 for two new Topeak racks. Not too bad, I guess... especially considering that they're being shipped from the States. Score one point for NAFTA!