All of the mass market companies make 90g. reef ready glass tanks.Aqueon,Oceanic,Marineland,Top Fin,Perfecto and they all will get the job done.
Personally,I would use only use a tank builder if I was looking for a custom size,euro-braced or rimless tank..For example,standard 90g. tanks are 24'' tall.If I wanted something around 90g. but more shallow ,say 18'' tall and 30'' wide then I would go with a tank builder.