Gas infrared heaters heat the object just like an electric infrared heater.
Depending on how much heat you want, here is some commercial installations that could easily fit your situation.
https://infraredradiant.com/patio-heaters/
This is just one brand that does it commercially.
The other and the easiest is the get some free standing propane ones. They run off a 20lb bottle hidden at the base and can be moved around where you need them. Here is an
amazon link to a host of them. Just do a search for free standing propane patio heater and you will get a whole bunch of venders and types....ie the round umbrella ones have been around for a long time, the pyramid ones are kind of new but add a nice flare to them.
https://www.amazon.com/s?k=patio+propane+heater&adgrpid=1343603773100076&hvadid=83975450735114&hvbmt=be&hvdev=c&hvlocphy=105382&hvnetw=o&hvqmt=e&hvtargid=kwd-83975578481984:loc-190&hydadcr=13737_13362720&tag=smokingmeatforums-20
Just looking at your space I could see a combination of both making you area fully functional for almost all conditions.
PS..Edit, the Patio ones are just larger versions of the buddy heater.....I have many of these, including a wall mount one in my shop.
https://www.mrheater.com/product/heaters/buddy-series.html