A IIgs power supply will physically fit in a IIe. Late model IIe's used the same power supply as the IIgs though with a different power connector. So to use a IIgs power supply the only thing you'd need to do is change that power connector.
Computers I have at least 1 of: 128k, 512k, 512ke, Plus, SE, SE/30, Classic, Color Classic, Mac II, IIfx, LC, IIci, Quadras 700, 800, 840AV, 900, PM6100, 6150, 8100, 6500, 7300, 8500, 9150, 9500, 8600, 9600, Beige G3 DT, MT, Server & AIO, B&W G3, Tray loading iMac, Slot loading iMac, eMac, G4 DA, Quicksilver
Mac Portable, Powerbooks: 100,140,145,145B, 160,170,180,190, 520C, 5300,Wallstreet, MacBook Pro
Apple III, Apple II: II, II+, IIe, IIc, IIc+, IIgs