Lot's of good bicycle forks out there that should be easily adapted and will put the Whizzer forks to shame. Swing by a good bicycle shop with your Whizzer and they should be able to tell you just what will fit. You'll probably have a hard time keeping that big steel front fender though.
I'd be worried about how well the Whizzer frame will hold up to the greatly increased braking loads. Might want to avoid frequent stoppies and save the new brake for emergencies.
Fsprandy the problem is the whizzer uses a threaded head tube and all mountain bikes above toys r us level use non threaded. I have a nice down hill fork Id love to put on it but I dont think it would work.
The older mountain bikes used threaded forks and it seems like they could be converted to threadless. Have you looked to see if there is a threadless headset available that will fit? If you get it to work let me know. The front "brake" on mine is the most pitiful piece of carp ever created by man. The forks are the second.
It's too bad Whizzer doesn't use the modern threadless headsets, but there might be hope. Back when threadless was new to BMX, some riders wanted to use the new 1 1/8" forks in their 1" frames. Someone figured out that you could take the 1" threaded Tioga MX-II headset to a machine shop and have the races milled out to fit the 1 1/8" fork, resulting in a 1"/1 1/8" hybrid headset.