Once you reach Level 14, you unlock Tom, who is a boy volunteering (initially at least) at your farm. Essentially, you can send him off into the wide world web to find other players selling items that you may need desperately. The first 3 days of his service, you can make use of him for free. He has a two hour recharge time, after which you can tell him to go and find whatever item you wish. He will come back with three options. You can then pay for the one you want, and he will go and fetch it, before falling asleep to recharge.
If you accept none of the items that Tom offers, he will only rest for 2 minutes before being available to search again.
After the first three days you have been using him, you will then have to pay for Tom's help using Diamonds. And it's not cheap. For 1 day, you are expected to pay 15 Diamonds. For 5 days, 60 Diamonds, and 10 Days is 100 Diamonds. So make use of him while you can!
Tom is great at ferreting out rare items