I'm not sure that the current design could easily accommodate 80mm fans and still work efficiently. This would mean increasing the width by 10mm on each side while maintaining the chamber as is. The fan I used is only $8.49 on Amazon.
To incorporate the larger fan, you would have to stretch the neck from the chamber to the fan and the fan to the nozzle. It would be better to just scale up the whole thing but that would require a different filter, etc. In general I don't share models because they generally contain proprietary functions but you can take the .STL, scale it to the size you want and reprint all the parts or simply trace the design, creating a new model of your own.