IF you want to go 1X this is pretty tough to beat https://www.ebay.com/itm/New-Shimano...sAAOSwUKxYdGuL

Otherwise just using any old shimano 9 speed shifter set should work such as https://www.ebay.com/itm/SHIMANO-DEO...oAAOSwQ4Rd-gXb

Just did a similar swap on a friends bike, switched out his old combo XT levers/shifters and went with SLX M7000 brakes. I had a set of old 9 speed shifters he used. But couldn't convince him to swap out his XTR rapid rise derailleur... oh well.