[TR] OT? Replacing Temp spare tires?

[Aribert Neumann]

Randall has mentioned using a compact temporary/narrow spare tire,
Txxx/xxR15, for use as a spare in a  TR3.    If I remember correctly from a
posting years ago,  Randall mentioned that he picked up a compact spare
(exact vehicle model unknown) at a salvage yard.

I would expect that the temp spare tires have the same dry rot concerns as
regular tires.  Can one buy new replacement temp spare tires?  Do the temp
spare tires mount on an existing wheel (do they have the same style lip)?
Are these tires easy to have dismounted?