I use a kind of seat that I believe is made for pedal-steel players, the guy that referred me to the maker of it called it a Pac-a-Seat (or Pack-a-Seat) ... it's a seat that has a storage compartment as part of it - very handy. I've used this for ~10-12 years, maybe more. It's basically a recangular box with its "lid" being the seat - with nice padding on it. The legs fold in, so you carry it like a small suitcase. Mine has 4 compartments in it and I carry my smaller items - shorter cables, mic, adapters, flashlight, etc. I just set it up at the gig, open up the 'lid', take out the pieces I need to set up my rig, then close the lid and "have a seat" and play! I can't remebmer who made it ... it was a smaller 'custom' kind of shop, again I believe he/they made stuff for pedal steel players. It is a fixed height, but I did some testing ahead of time, and it was a perfect height for me (and was a good height when I used to play MIDI organ-style pedals along with my keybaords).

Jim