Get parts of transaction that need to be signed by the users private key

I’m looking to get the piece of raw data that needs to be signed by the users private key as demonstrated in this bitcoin.stackexchange.com question:

https://bitcoin.stackexchange.com/questions/3374/how-to-redeem-a-basic-tx

I want give the user the abillity to copy and paste this text into their native desktop wallet and use the ‘Sign message’ feature to complete complete the signature for the transaction.

The motivation for doing this is to decouple my service from the control of the users private key.

Is there a way to do this with Bitcore?