If you just need to update the inventory quantity, our app EZ Inventory might work for you.
You can set up a separate "Data Feed" setting for each supplier and schedule each one to run as frequent as every 1 hour. We do support CSV, Excel, XML, TXT formats. The data/inventory file can be pulled from an FTP or SFTP server, a website URL, or just manually upload the file.
Please feel free to reach out to us if you have any questions!
My name is Alison, and I'm the Customer Success Specialist for Ablestar.
Our Bulk Editor app, https://apps.shopify.com/bulk-product-editor, is capable of updating inventory using CSV or XLSX files, and on the Professional Plan, it is also capable of downloading and processing inventory updates from FTP sites, DropBox, etc.
If you have any questions you can reach us at 'email@example.com'.