Is there a way to trade off amperage for voltage?
You can very likely find a pre-designed car adapter that is compatible with your laptop as an accessory. This can use a 12V battery as a source. Internally these adapters will use a step-up conversion to make the appropriate voltage for your device.

Here's an example: https://www.amazon.com/Universal-Charger-Adapter-ThinkPad-Computers/dp/B07FY9TXNV

EDIT: based on your additional info (135W @ 19V, Acer laptop), here are some suitable 12V-in chargers: https://powerstream.com/ADC-ACER.htm.