I do not see the bolt holes as a high wear area. I think they were simply built with a loos fit. My 4 step setup are not loose, and they were manufactured in 1988.
I did not consider plastic bushings. You might find plastic tubing with a 1/4" ID, and simply cut to length with a box cutter. Drilling just a 1/32 oversize hole and using poly tubing as the bushings might work.
While I only know first hand of one person that drilled oversize holes, they said it worked for them. They made no mention of oval holes being an issue.
No question, a set of new and better designed steps would be the best fix. However, what would new steps cost, and do you have more time than money? You only need to drill a couple to see if the fix will work.