Amazon offers the Gillette Fusion Manual Men's Razor Blade Refills 12-Count for $29.95. Clip the $6 off coupon on the product page to knock it to $23.95. Prime members qualify for free shipping. That's $6 under what you'd pay at a local store. They're compatible with Fusion5 and Fusion5 Power razors.

Update: Free shipping is available for all customers.