I found the gears on an online bike shop . They weren't too expensive but I did go with a higher quality brand to make sure they would look nice. I believe I spent $14 on each gear. The clock parts I got at our local Michael's craft store for about $5.
I used a craft glue called E-3000 secure the clock parts to the gear. It isn't a tacky glue so you must set the craft where it won't be easily moved around. Make sure it's sitting on a flat surface. Let it sit for at least 5 hours before trying to pick it up. I let mine sit for about 12 hours just to make sure.
The boys liked their clocks more than the other gifts I gave them and that made me feel GREAT!
I love making things for people and this project was a huge success. You can find gears that are less expensive but I thought this style looked good.
TA-DA!