Can i find a lucky egg in diamond?

Question

If so where? or does the lucky egg only start in platinum?

Answer 1

You can find it. It's held by wild Chansey. 5% chance.
Chansey is found at Routes 209, 210 and Trophy Garden.
Source

Answer 2

Well you have a 5% chance of finding one on a chansey and that is the only way.
So catch lots of chanseys or use snatch.