Sometimes you can use floral type ribbons, which are usually wider 1"-2". The thin copper wire at the edges can be pulled out (I recall tying one end of the wire to the metal door handle, and then slowly walking backwards, smoothing the ribbon over the end as I go). And being larp, (cf historical enactments) we don’t mind if its synthetic.
You could try composite ribbon - add several thin ribbons with a gap in between to give the appearance of a wide border.
Or make you own ribbon - get length of patterned material and sew it to the dress with a close satin stich - like the button holes.
But in that case, only add the ribbon to the bodice / neckline - I’m sure you don’t want to be doing huge lengths to do around the hem.
Otherwise, I’d be interested to see what others suggest too.