Gotta love Cateye. I own hundreds of dollars worth of various different bike lights (nite-rider, cateye, vistalight, others... I know, it's too much!)
but get this...
Cateye's small parts catalog is extensive.
I payed just .87 cents shipping on a second mounting bracket that was reasonably priced at $5 bucks.
https://www.cateye.com/store/index.php
ps. the bracket I ordered is for an el-320 that is almost as good at making me visible to motorists as my nite-rider digital. One cost $35, the other cost $250. The battery life with the el-320 is about 40 hours on full, 100 on blink, compared to 2.5 hours with the niterider digital on blink or full. Guess which one cost less?
pps. On the other hand I would take the niterider on a totally dark street or off-road ride in a second it casts a nice long and full beam. The el-320 is more like a blinking camera flash.