Portable Tool Kit - what works best?

Rolling toolboxes with drawers are great in the shop, but a lot of my wrenching is done away from the shop, outside in a parking lot nearby.

I've tried a couple approaches - carrying out only those tools I need for hte job (and making multiple trips back for things I didn't know I needed). I tried a tool bag but invariably spend so much time digging for the right wrench and not finding it even when it's there. This led to carrying several five gallon buckets around, which just spreads the problem out more.

Does anyone have any great solutions they've found for an outdoor wrenching situation? A small rolling cart? Better organized tool rolls?

Sounds dumb, but this is holding me back from getting stuff done. Would love to hear what others have found that works for them. Thanks!