While I neither have use for one (I use a small step ladder for my newt) nor the inclination to build one I've seen many a plan for building them out of timber that didn't look overly awkward or complex if you have basic wood working tools and the health/time/inclination.
Worth a look if you're in a position to knock something together much cheaper than commercial units. Crater101, I'm talking to you, lol.
https://www.jerryoltion.com/observing_chair.htm
https://www.skyatnightmagazine.com/a...bserving-chair
https://www.cloudynights.com/article...ng-chair-r3098
https://www.denverastro.org/wp-conte...verObsSeat.pdf
https://stargazerslounge.com/applica...t.php?id=32496
I didn't look at a lot of these but I would assume the materials list wouldn't be overly costly or hard to knock together health, time and inclination permitting.
Worth a look if you're in a position for a little DIY.