where can i find replacement spring?

You say precious little about the spring you seek - compression or expansion - approximate dimensions - so it's a big guessing game for anybody foolish enough to try and help you - they would be bound to get it wrong.

However...

Here in the UK Amazon sell springs - singly and in kits.

Perhaps it's the same where you live?

Also - if you use Google and select Images on the top left and enter Metal Spring you'll get images of many springs - when you see one close to what you need you can follow he link and maybe get lucky.

Be sure to enter metal spring - if you just put in "spring" you'll get lots of pictures of flowers.

Good luck...

Peccavi
April 2013