those look exactly like the seals on a couple step vans i have had over the years, i would go to a local glass shop that installs, take one of the seals out and take with you, they can match it up and give you a crash course on installing....... very simple and fairly easy with flat panels....
there are numerous videos on you tube showing how to measure/cut/replace
just for fun get price quotes from a marine supplier, and a local non marine related glass company....... you could also match it up with an on-line supplier and go totally "self contained" with the project
here is one example of what you would be looking for...
here is a few different designs and the tools(not needed, but helpful)