26 x 1 3/8" wheels aren't very common anymore. Cheap replacements are available at any bike shop.
I wouldn't waste your time making it into a fixie. You'll have to have a custom handbuilt wheel made- this is not something that's available off-the-shelf. By the time you pay for that, you'll spend more than you paid for the whole bike to begin with.
$40 for an old Randor (I think this was a division of Raleigh way back when) is a lot. I think they sold for $120-150 when new.
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Jeff Wills
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