Backup Boot SD card without it being a 1:1 full SD card copy?

Anyone know a way to make a backup image of a currently used SD card that isn’t a 1:1 copy of the entire SD card, including unused space/etc? In this case specifically for a BPI running OpenWRT but also just in general for PIs on Linux/OpenWRT/PiOS, etc… I have quite a few Pis of various sorts and always just boot from the SD cards on all of them, but want to be able to keep a repository of their images so when a card gets corrupted I can just flash a direct copy and keep going… however, the 1:1 method 1) requires way more space than it should (not a huge deal, but still annoying) and 2) doesn’t work unless the 2 SD cards are identical in size so I’d like to be able to just save a snapshot of the device at a given time (and not a copy of the full 32/64/128gb SD card I’m using because I have so many and they are cheap) I can than use an imaging tool to put on a new SD card.