As one of its daily deals, B&H Photo Video offers the Kensington Trackball 4-Button USB Expert Pro Mouse, model no. DZSPKEMEPU, for $39.95 with free shipping. That's tied with our mention from last winter and the lowest total price we could find by $20. It's compatible with Windows 8 and features DiamondEye optical tracking technology, scroll ring, and detachable wrist pad. Deal ends today.