Explore websites that specialize in industrial machinery sales, such as Machinio, EquipNet, and evomatec.de
Auctions:

Check out industrial equipment auctions, both online and offline. Popular auction sites include Bid on Equipment and Equip-Bid.

Manufacturers and Dealers:

Visit the websites of CNC machining center manufacturers, as they often have sections for new or used equipment sales. Additionally, authorized dealers may have listings or can help you find what you need.
Local Machine Shops and Trade Shows:

Contact local machine shops or attend industry trade shows and exhibitions. Networking with professionals in the field might lead you to opportunities to purchase used equipment.
Classified Ads:

Check classified ad websites, both online and in local newspapers. Sometimes, businesses or individuals sell used machinery through these platforms.
Industrial Surplus Stores:

Some areas have stores that specialize in surplus industrial equipment. Check if there are any in your region.
Networking and Industry Forums:

Join online forums and communities related to CNC machining or manufacturing. Members often share information about equipment sales or may have recommendations.
When searching for CNC machining centers, be sure to consider factors such as the machine's condition, specifications, maintenance history, and the reputation of the seller. It's also a good idea to consult with experts or seek advice from those experienced in CNC machining before making a purchase