Search on Craigslist, Ebay, Offerup, etc.
local swap meets may be a source too...
hint: they won't be cheap unless they're messed up.
and they are plastic, not "mag"... you might be confusing 5 spoke wheels with the term "mag", which really relates to magnesium cast wheels.. see: "snowflake BMX mags"
the 5 spoke BMX wheels made of metal are aluminum cast wheels, and they are heavy junk.
starting your search here won't net much, but hey, it was worth a shot.
