I have powered a pedalboard tuner plus TC Electronics successfully from a 7800mah powerbank using a 5v to 9v converter cable from MyVolts. Lasted a pretty long time (at least 8+ 45 minute practice sessions before needing to recharge).
You could always try their Platinum range with a hexagonal core. They are physically very smooth feeling with a decently high tension and produce very pleasant fundementals. There is a video demonstrating all the bass string variants on their website.
I have just put a set of the new nickel 46 - 100 Shorties on a bass and they are sounding really good.
The Leathergraft I have has five slats in the ladder Schlippy. I also asked for a specific length between the end keyholes (104cm as I am only short😁) which cost an extra £5.
Have my bass so that it is at the same height sitting or standing which works out at 104cm on the 'custom' Leathergraft strap I use.
As you can probably guess I am not very tall