I am sure there are swap meets in both states.
They are sometimes put on by MC clubs.
But sometimes by a private promoter.
And are unlikely to be listed on the net in most cases.
You need to find a few guys riding old motorcycles and ask them.
Or try a MC dealer (but young guys don't know shit.. or his brother).
In IL try the IMDA website maybe?
In PA I know there is a vintage swap meet by the 'White Rose MC club" (or some such name.. don't know location).
They usually hold them twice a year (spring/fall?) at the chosen location.
Like a hockrey arena or civic center or 4H fair type of location.
You will have to beat the bushes and ask around.