Most any antenna will work on a Kaiser, however, if you want them to look period correct, you'll want one with an extendable mast. Also, KF used an antenna with a long extension that sat inside the fender that also had a strap that tied the unit to the fender at the bottom. Without this, most inexpensive aftermarket units tend to slip on the Kaiser's curved fender and won't stay upright.
The Pontiac antenna is the closest match I've seen in a long time. The 90 bucks seems steep but is cheap compared to the $250 that the last NOS KF antenna fetched on ebay.