I always just make the keys myself. Sometimes I have been in a hurry,and just made ROUND keys on my lathe. They can be made from drill rod and hardened. For home shop use,they work just fine and last many years(I never have had to replace one). Obviously they are by design,inferior to rectangular keys,but they have worked fine for my use on a few vises. Make them a snug fit in your table's slots.
This assumes that your mill table's slots are in fine shape,and free of stray cuts,etc. that would make round keys not work.
Most of the time I just take rectangular stock and mill it down to make normal keys. You might want to try the round ones too.
$150.00 odd is a fantastic deal!! Fill the sand holes with some JB Weld and they will not be very noticeable.