Drop a fiver on one of these:
https://www.amazon.com/gp/product/B0...hps_bw_c_x_3_w
You’re right to be wary of non-alkalines. I once seriously blew a showcase gig when I tried using a lithium 9v. Fit my Martin’s battery slide but did not make electrical contact. Extremely embarassing. Had to borrow the headliner’s guitar. I thought I was gonna die from shame.