Dell Small Business offers the Logitech K750 Wireless Solar Keyboard in Black, model no. 920-002912, bundled with a $20 Dell Gift Card for $59.99 with free shipping. (The gift card appears in cart and will be delivered via email 10 to 20 days after shipment.) Outside of the price below, that's the lowest total price we could find by $10, although we saw it for $4 less in February. This wireless keyboard is powered by light and measures only 1/3" thick.
Don't want the gift card? 6ave via Rakuten offers it for $41.30 with free shipping.