Not a way to find it , but to document that it's not possible from Google Dashboard anymore
Is it possible to find the IMEI number of a lost Android phone using Google Dashboard?
Google removed this feature for reasons best known to them. From Google Support, see what
As catzrule states, Google has was removed IMEI information from the new dashboard view.
Google is considering where and if it might be appropriate to re-surface that info.
You can leave Feedback
about this with Gmail.
This is the latest official source (October last year) I could find, so there is no way out unless you have the box or bill mentioning IMEI.
If you synced to itunes as claimed here ( I can't confirm)
Another very long shot is if you had installed a paid app that is single device use and is linked to your IMEI number (I have a call recorder app that does this and everytime I change my device , need to mail them with new IMEI number, so end up having a record)
As Bochur mentioned in comments (thanks), asking Telco is another possibility
I wish Google would reintroduce this
Edit Things that didn't help
Chatting with Google help from Play Store options - they were totally clueless and couldn't direct me to somebody who can help
Downloading data from Google Dashboard. Combed but to no avail. Only interesting thing is that you can see your Google ID here