Where do I find a diamond for the time machine?

Hint 1 of 6:

In times like these, it helps to try relaxing with a little television.

Hint 2 of 6:

That home shopping show has just the diamond you need.  All you need is the
money to pay for it.

Hint 3 of 6:

Dr. Fred told you something about a contract over a computer game.  It's
worth a lot of money.

Hint 4 of 6:

The contract is in the safe.  See an earlier question in this section if you
don't already have the contract.

Hint 5 of 6:

What to do with the contract is also covered in another question.

Hint 6 of 6:

Once you have the money, all you need to do is use any phone.  The diamond
will be delivered and left next to the mailbox.  Don't forget to pick up the
Swiss bankbook from Dr. Fred's desk so you can pay the operator!