I haven't been to a gun show in years but my kit is still here and ready to go...

Cotton gloves.

Wipedown cloth

Skeets bore gauge

Bore light

Chamber gauge

Cleaning rod, patches, etc., I filled empty eyedrops bottles with Hoppes, etc.

AA Magnalite w/fiber optic extension

Small tape measure

Pen and pad

Plastic digital calipers, with the bore gauge I could get an in-exact idea of wall thickness, OD minus ID /2

Book of proofmarks

Set of Magna bits

Cash

My contact cards.

Copies of my C&R FFL, if you dabble in old guns, well worth it.

I also carried books about Savage 99's, Winchester Handbook, etc.

Gun sock

These days I also would carry the $30 borescope I got on Amazon that displays on phone or pad.

I also carried a copy of British Proof Laws.

Everything fit in a shoulder laptop case.