I realize that the OP is well intended with their recommendation of this item, and I am sorry to have to be the voice of disagreement here but, by trusting a <$15 suction cup device, one is risking a broken hip or other bodily injuries.
Yes, in theory and practice it works today, but even the smallest amount of dirt under that cup, or an imperfect sealing (see the reviews) can weaken the seal and send one into the condition referred to in the medical field as "A$$ over teakettle". I would only trust my health & safety to a permanently attached assist handle that has a back-up panel on the inside as well.
Here's a link to the product shown:
Glacier Bay 12 in. x 1-1/4 in. Suction Assist Bar with Suction Indicators in White-GB-SUC12-01 at The Home Depot
In the product description it's clearly stated: "Use for stability only" i.e., it's not intended to be a weight
supporting device as it could be, especially when using it when entering ones trailer.
BTW: Pulling sideways on this devices is a worst case scenario.
A standard 18" to 24" assist bar, permanently attached to that wall, would be much safer