Green’s Dictionary of Slang

one who is slavishly devoted to following the latest trends (but never quite achieves the correct effect).

1986		C. Stroud Close Pursuit (1988) 18: Even a few tough trendoids from the East Village [...] have been forced into the region by gentrification.
1999		N. Cohn Yes We have No 159: You’re sick of being sneered at by a bunch of London trendoids.
2005		D. Vandenberg Iron Circle 31: [T]he slumming Euro-trash trendoids jazzed up on hard drugs .