Step 1: Acquire fifty one-dollar bills. If you're feeling especially rich, mix fives and tens in with them.
Step 2: Put them into a random order.
Step 3: Generate a password by taking the least significant two digits of each bill, in order, for a 100-digit number. Use this password to encrypt your data.
Step 4: Make sure that the bills never get out of order. Keep them in your desk drawer or another safe place.
Step 5: The cops raid your place. There is a decent chance that a small stack of cash would never make it into evidence, simply vanishing into an officer's pocket. Even if that doesn't happen, they'll catalog the money, sort it (here's where the fives and tens come in handy), and almost certainly get it out of order in the process.
Step 6: Your password is now gone. Unless the cops turned in the cash and kept it in order, it is impossible for you to tell them your password. If the bills make it into evidence, there are up to 50! (~200 bits) possible passwords. If not, there are 10^100 (~300 bits) possible passwords.
Step 7: Don't actually do steps 1-4. Just keep a small stack of cash next to your computer. Your actual password can be your cat's name. Just be willing to testify under oath that you did steps 1-4.