Welcome to the County of Riverside Vendor Registration Portal. To work with us, you'll need to first register as a county vendor.Click here to visit the Riverside County Purchasing and Fleet Department. The vendor must download the Vendor Agreement from the attachment tab, fill in the requested information and upload the completed agreement. Riverside City College. 4800 Magnolia Ave Riverside,. Email invitation link takes supplier to the Welcome Page of the Supplier Registration. To set up as a new vendor, please sign up through the sign-up link and download and fill out the Vendor Agreement form, which can be downloaded below. How to fill out the Vendor Agreement for Services and Compliance? Vendor is required to sign and submit a Festival of Lights Vendor Agreement.