Flight Deck Seats

As previously mentioned, using your intended seat or building the seat for a flight deck early on will save time in refining heights if you use a temporary expedient.

Car Seats

Car seats can have the advantages of an adjustable track, backrests, armrests, and being well upholstered. If you go to a auto recycling center (a.k.a. junk yard), they will want to know what seat, including year make and model of the car. Its a good idea to cruise the used car lots and sit in some cars to see what seats might work for you. Spacecraft generally have very upright seating, so van and truck seats ("command style" seating) would be a good place to start. You can probably find something workable between $25 and $150.

Yagni01 uses a late model Toyota Camry driver seat. It has adjustable lumbar support, but no armrest.

Building an Airliner Style Seat

There are plans for an airliner type seat you can make out of wood here