I bought a large box of Allen keys years ago, and have bought more as the box kept hiding so that these days, if I can't find the box set, there will be others in the back of cupboards, drawers or in the shed somewhere. I've also started keeping all the tiniest keys that come with attys in their boxes, just in case etc.
The hassles are now being caused by certain drippers having shit posidrive type (Philips, etc )screws that even the ubiquitous bloody screwdrivers (blue) that are supplied with the fucking device, don't bloody fit. Or the bloody screws aren't actually long enough to trap the wires so I have to use a piece of old coil wire to pack the post hole.
Atm, one of the Allen bolts from an unused dripper is being used in an RDA that has posidrive screws thus making rebuilds a pita as I need screwdriver AND Allen key. Grrrrrrr.