Well, my apologies as I stand corrected. It looks like the company has existed for a while. With the sheer number of "companies" barfing power banks into the supply chain, it's not too difficult to jump to such a conclusion, though. Especially with a round window and button on the side being such common design elements:

https://www.amazon.com/ROMOSS-40000mAh-Portable-Charging-Microsoft/dp/B0B4SJTXZD/

https://www.amazon.com/30000mah-Baseus-Portable-Charger-Charging/dp/B08JV4W4NY/ (Yes, I know Baseus isn't a SIXLTR, but you get the idea.)

Also, it's SIXLTR, not SIXLRT, and it's not an acronym.

I use this to power my full nano Caixa case, a Beatstep pro and various usb things all at once:
https://www.amazon.com/dp/B0B4SJTXZD?ref=ppx_yo2ov_dt_b_product_details&th=1

For powering the rack you need a 15v usb-c power delivery to barrel connector. I use these:
https://www.amazon.com/dp/B08NS491XW?ref=ppx\_yo2ov\_dt\_b\_product\_details&th=1