315 was Ryan
320 was Chervon (Asian) per the list. They might fit, but I'd be surprised.
I'd measure the hole size, and look at what you have left for attachment points, and start Google searches for something similar or bigger, then file or sand down.
My Ace has loose brushes in a compartmentalized box also. Maybe search a bit further than your local hardware, or search Aces website, and find the closest in stock.
eBay has options too
Model: carbon brush 10pcs. Product alias: Brush electric grinder small spring carbon brush. Type: carbon brush. 10 Carbon Brush. Material: carbon. Number of teeth: None. Our goal is to provide you with the best service.
www.ebay.com