Michael, Magpul would be your best bet. Kci would probably be the second best. Buds doesn't have any Magpul ones in stock but here's a kci drum if interested.....budsgunshop.com/product_info.php/products_id/713087438/kci+usa+inc+magazine+for+glock+9mm... Hope this helps.

Michael, this model uses Glock and Glock style Magazines and Drums. The kink of the hill is the Magpul Drum here : https://riflesupply.com/Magpul-Industries-PMAG-D-50-EV9-Drum-Magazine-50RD-9MM-Black-MAG1035-BLK_p_5779.html

This uses Glock pattern magazine. KCI Glock drum mag is probably the best one out there right now ( budsgunshop.com/product_info.php/products_id/713087438/kci+usa+inc+magazine+for+glock+9mm ) But most of them (especially promag) is unreliable. If you can wait, I would wait for Magpul D60 Glock mag to come out. I hope this helps!