Re blank vinyl calibration record:
I think one might use an old CD that way!
Although I do have some old DG albums that take up three sides of two disks. The last side, that says in German, something like "Achtung! No musik recorded here!" does have grooves (with a weird pattern to them - I really should try to play one like that one day) and would thus be useless for this job. If you have to go that way I'd use a CD or a 12" LaserDisk if you remember them.
And to the OP: you should be sure that your cartridge is the rate-limiting factor before spending money there.