Professional tripods use quarter inch screws to fix your camera in place. You can easily source a screw of the same size from a normal hardware store. To avoid travelling with a bulky tripod, drill a hole in a standard bottle top (the type you d find capping a 500ml drinks bottle) and thread the screw through it, fixing it in place using strong glue.
Keep this in your camera bag as you travel, but don t bother carrying the rest of the bottle, as these are easily sourced wherever you happen to end up. Fill an empty bottle with grit to give it some weight and screw your cap to the top. Instant tripod.