Seeing as how it's an SMC Solenoid valve, I started with the SMC Corporation website.
SMC Corporation
Following their product descriptions, I found
this page which lets you configure the exact solenoid valve you want. By choosing the correct options, I was able to recreate the SY3140-6H-S part number supplied in the kit of parts.
SMC probably has a distribution network, so you may be able to find a local distributor of their products. Armed with that part number, I think you'll find what you're looking for. Hope this helps.
Bengineer