i have a pair of fritschi brakes (i think they are actually the 85mm brakes) that work OK on spatulas, which are even wider.
one easy way to do it is to put a boot in the binding (i.e., retract the brake), then use the circular end of a combination wrench to bend the brake arms so they curve outward. there won't be a dramatic 90* bend but, rather, a more gentle curve.
if you are starting with the fritschi 100 brakes (which are actually about 108mm when you factor in the height of the fritschi), then it should take very minimal bending by the method i describe above.