EDIT: The sweep tool did not actually fail. It returned an error code but the transaction went through. It can be found here: https://github.com/Jpja/Sweep-XCP-Paperwallet

I have a private key to a BTC address containing SJCX, but not a passphrase for an associated Counterparty wallet. The "sweep" function is commonly used in this case, but users have reported problems with it for some time: https://counterpartytalk.org/t/problems-sweeping/643/24

None of the solutions posed there or elsewhere worked for me.

So is there any other option for me than syncing the whole BTC blockchain or giving up my private key to someone who has?

I'd hoped to find a tool such as this that works: https://github.com/Jpja

Unfortunately the "sweep"  tool there also failed in my case.

Thanks.