I think the only option now is the MDT mags for 6mm ARC: https://mdttac.com/6mm-arc-mdt-metal-magazine-10-rnd/
or the 12 rd mags …. https://mdttac.com/6mm-arc-mdt-metal-magazine-12-rnd/
or the 12 rd mags …. https://mdttac.com/6mm-arc-mdt-metal-magazine-12-rnd/