You can take one of the already built 17mm ATtiny13 drivers, just not put the ATtiny13 on there…then jumper pin 6 to the bat +
As soon as the clicky sends power thru it…the light comes on (more or less an always on signal to the enable pin on the regulator chips), 1 mode…wide open but regulated thru the 7135’s
If you want to “learn” how to do it…Mattaus has done a VERY good howto video series on building drivers
Or do you want to just have the full 105C, programmed with a full 100% on firmware so you still retain low voltage signalling and reverse polarity protection?
It would be cheaper to not have to put the MCU on the board if you want a single mode always on driver…