https://www.easystepsystem.com/
My partner has one of these. <$400, easy to install (he did it himself and he is not mechanically inclined). Makes boarding, disembarking much easier. One caution - depending on where you have to mount this on your trailer it could affect your turn radius. My partner learnt this lesson the hard way, cost him some $$ to get his rear bumper repaired.
There is no doubt someone in your area could fabricate something like this for <$400. May be the better way to go - he could spec it out to match your trailer/tow vehicle, avoid the rear bumper issue.
