So I ended up just buying the zinc plated steel rod at home depot and turning it into an axle tonight. Went pretty well except my WD40 leaks about 10 parts out of the cap for every 1 part you spray out the straw. So I made a real big mess while drilling but oh well. It came out descent.
These pictures look very similar to the second picture on the original post. But in this picture, the wheels are installed with the newly fabricated axle and they are ready to go. I also rounded the edges of the axle on a bench grinder. Since they stick out further than the wheels, hopefully this will prevent them from catching on things when i'm up close.
Now I kind of want to replace the front wheels. They're not worn out and I can't go any bigger up front because it will rub on the vacuum sucker part. But now I want front wheels that match the rear wheels in color and shape