The blockchain for SYS1 is dead since many years and it would not really help you if you find that address. You could see the coins but not get access to them.
The Syscoin address is only the public key.
You need the private key stored in your wallet to access the coins.
You need to open that wallet.dat with a Syscoin core version for SYS1.
I believe the latest of that line was v1.5.1.1 from 30.04.2015.
It does not need to synchronize (it can’t since the chain is not active anymore).
You still can see the transactions the wallet has recorded, the keys and the amount of coins.