Piece of cake. Go to your fuse panel single spade connector to Radio. It is switched hot after the key is on. Run a hot to the dash put in a simple switch and run it across the floor under the carpet or hide it and up to the fan mounted on the roll bar or something. Ground it locally so you don't have wires all over or just pair a good chassis ground to the power wire to the fan.
89 2.5 TBI, 4" RC lift, 1" Booms, SYE, Adams Driveshafts front and rear, Ford 8.8 with 4:88s, BFG 33X12.50X15, and a ton of other stuff.
AF Jeep Club Tail Number 184