The part list is short. Get the PCB GERBERs and order the PCB from any manufacturer. THis will be quite cheap. Once you have the PCB get all the parts below. You can solder the ATtiny85 directly on the PCB but is better to use the 8-DIP socket so we could remove the chip anytime. The LED could be of any color that you want. The rest are basic components. Remember to order a CR2032 battery as well.