We don't have synonyms for flannelet yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are flannel, lancelet and flanneled.
(n) :
Alternative spelling of flannelette. [A type of soft, woven fabric, made to imitate flannel by raising or brushing the fibers in the weft. Frequently used in sleepwear, pillows, and bedding.]
(n) :
Alternative spelling of flannelette. [A type of soft, woven fabric, made to imitate flannel by raising or brushing the fibers in the weft. Frequently used in sleepwear, pillows, and bedding.]