On a budget, want a flashlight for my shotgun.

I want to put a mounted light onto my shotgun. It's an 870-esque 20 gauge pump. It doesn't have any rails on it so I see two options. 1: buy a tube/barrel mounted flashlight. 2: buy a tube/barrel mounted picatinny rail and then buy a flashlight holder that mounts into a rail.

I'm not looking to break the bank here and have a budget of about $60. Any general ideas or specific gear recommendations would be appreciated.

A small Maglite and some good duct tape.

1" Light Mount : TACTICAL SHOTGUN MOUNT | Brownells

$33, use with mag light w/tailcap or other flashlights