Technically you can use any Mineral Oil since there is no governing body. Mineral Oil brake fluids are not governed by any standards or regulatory body, whereas DOT brake fluids are governed and have standards.
Your best bet would be to use mountain bike hydraulic brake fluid / mineral oil. You'll also need a bleed kit while you're at it. Something like this is an all-in-one solution - includes a bleed kit and mineral oil:
Amazon.com : Revmega Bleeder Hydraulic Disc Brake Bleed Kit Tool fit Shimano - Inc. 60ml Mineral Oil Fluid : Sports & Outdoors
www.amazon.com
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