Lost key
 

I pururesed a u lock for my bike a few days ago and I lost my keys how do I get a replacement key

What brand? Is the lock hooked to the bike? I think Kryptonite will sell keys, but are somewhat specific with the procedure so that you can't just buy keys for locks you don't own.

Anyway, contact the lock manufacturer.

A good locksmith could probably open your lock, and may be able to make a key if they have the blanks available. Whether it is worth the trouble depends on whether it is a $20 lock or a $100 lock.

You should have had two keys. Don't keep them together.

If you carry a keychain, put the key on the keychain.

I have a stripped out tiewrap that I use to attach my key to the lock when not in use. The lock is carried in a backpack.

Either the keys or the tags on the lock will have the key code number for that lock. Is there a serial number someplace? I hope you wrote it down. Otherwise, there's no way to know which key will fit your lock.