To obtain the necessary Testnet SUI tokens for connecting Walrus to SNS, you can use the SUI discord faucet, where you can request a few SUI every several hours. Typically, you need around 3 to 4 SUI to buy a domain on the SNS testnet. Therefore, with some patience, you can gather the required amount in a day. You might also consider the CLI utility provided by Walrus to convert Testnet SUI tokens into Testnet WAL tokens, using their command walrus get-wal. Keep in mind that both the tokens are testnet tokens and have no real-world value.

If you want to avoid the waiting time, setting up a local Walrus test network on your system as detailed in the Walrus setup documentation could be beneficial. This way, you will not be bound to the faucet constraints for testing purposes.