Personally would not even consider the suction type bar....they do come loose and then you could have a real problem.
Our DS#1 has an assortment of health issues and uses a shower bench at home and we just take it with us when he comes along. He had the longer one that fit outside the tub, across and into the inside, but obviously that wasn't going to work in the TT. Headed for Walmart and they have a surprisingly complete home health products section. Think this one, which supports up to around 350# was around $23. We have the 34" corner shower and this fits perfectly. Think it would also be fine in the tub type, but if you have the smaller corner shower, likely should do some measurements.