We don't have synonyms for shell suits yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are shell suit and shellsuit.
(n) :
(chiefly UK) A lightweight tracksuit consisting of a zip-front jacket and matching elasticated trousers, each having an outer nylon shell, often bearing panels and flashes of different colours, and inner cotton lining; popular in the late 1980s and early 1990s both as sportswear and as general leisurewear.
(n) :
(chiefly UK) A lightweight tracksuit consisting of a zip-front jacket and matching elasticated trousers, each having an outer nylon shell, often bearing panels and flashes of different colours, and inner cotton lining; popular in the late 1980s and early 1990s both as sportswear and as general leisurewear.