You can pick up a basic Cateye comp for $20 or less, probably locally.

Personally I use a Planet Bike Protege 9, though the 8 or 5 would be fine for you too. I just mention it because even though they're a bit more expensive, they are very durable. I've had my 9 for about 7 years now.

You're going to get a certain number of functions simply because it costs exactly $0 to implement them. Clock, speedo, average speed, max speed, trends, etc cost nothing, they're just programming on the chip, so taking them off wouldn't save any money, so they'd just be putting themselves at a competitive disadvantage by selling such a computer.