This open access paper uses what is described as a Drosophila dfmr1 null mutant strain, dFmr1-Del3-21/TM6C, Kr:GFP.
Xu S, Poidevin M, Han E, Bi J, Jin P. Circadian rhythm-dependent alterations of gene expression in Drosophila brain lacking fragile X mental retardation protein. PLoS One. 2012;7(5):e37937. PubMed PMID: 22655085; PubMed Central PMCID: PMC3360013.
See also BDSC's fly stocks page for Fragile X Syndrome.
And a past post on a paper linking the circadian clock to neurodegenerative disease.