Machinedrum SPS-1 MKII - Battery Pack?

Has anybody found a battery pack that can safely power the Machinedrum SPS-1 MKII? I’m having a hard time finding a battery pack with 6V 3A output.

There are some posts in here that could help. Since the OT MKI apparently also needs 6V 3A, look for info on that too.

6v 5 amp
BR-CCF2TH, 6 Volt, 5000mAh Lithium PLC/Industrial Computer Replacement Battery (onesourcebattery.com)

6v 3 amp
6V, 3Ah LFP Battery (PVC, BLF-0603W) – Bioenno Power

you could also run these 2 in parallel to get 6v 3.6 amp
Amazon.com: WELLVEUS 2CR17335A WK17 6V 1800mAh Lithium Battery Compatible for SANYO MR-BAT6V1 2CR17335A WK17(Pack of 2) (CR17335) : Health & Household

6v 4.2 amp
Onyx 6.0V 4200mAh Sub-C NiMH Flat Receiver Battery: Universal Receiver | Tower Hobbies

though these may not be the kind of battery pack you’re looking for, these are the kind which are available.