Almost any bike computer can do speed and distance. You can pick up one at any bike shop.

Most work by placing a magnet on one of the wheels and putting a sensor on the front fork or chain stay in the back.

The cheaper bike computers use a wire from the pickup sensor up to the mount on the handlebars. More expensive computers are wireless so you don't have to mess with the wiring.

These computers require that you set the tire size into the computer to get accurate measurements.

You could pay the bike shop to install it for you.

If you want something fancier, you can get GPS bike computers which don't need a sensor.