Not a Lakland owner but would point you in the direction of Newtone strings who can wind bespoke gauges for you and also offer options such as steel or nickel, standard or fine outer windings and round or hexagonal cores. You should be able configure almost anything you like (except flat wound).
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.