"Camp chairs" for folks in the 1770s would have been large rocks, logs and the ground (maybe with a couple hides under you.
The slat chairs many folks use today are a 1970s re-enactorism.
There were chairs, but mainly for military officers. I'll see what I can dig up for you.
My other thought, well advice, is research before you buy. Saves a lot of money in the end.
Mario