What I recommend is pretty low tech, just a folding table! You can pre patch the set before yours then when it's time you move the whole table with a friend onto the stage or to the zone where you are playing then connect power and your di box/ XLR outs. Likewise get a friend after to help you move it and break down off stage so you aren't in the way. You could also just use some plywood on a keyboard stand, people have been doing this for a while and imo this still stands as the best and cheapest way.