If you want a lightweight seat that is also safe, you need to spend some money and buy an FIA approved seat or either go with the Ultra Shield or Butler Built racing seats.
Ultra Shield and Butler Built builds the seats for all NASCAR series cars and also have drag racing seats. Also, ISP is a well known manufacturer of drag racing seats for Top Sportsman, Pro Mod and Pro Stock.
https://www.butlerbuilt.net/prodrag-plus
https://www.butlerbuilt.net/prodrag
https://www.ultrashieldrace.com/cata...ec-miata-seat/
https://www.ultrashieldrace.com/cata...ly-sport-seat/
https://www.ispseats.com/drag.html