If no modulation is needed, why not using class E with an ordinary silicon or SiC FET?
You don't need super low Cds, nor super low Cgs (providing Rg is low).
Basically any device with a good gate runner design and no intentional internal Rg will work fine.
Thanks you

So... i'm reading some book's (
some are from soviet union and some are from united states) from 60's,70's and 80's and there's plenty of fun projects like :
Plasma generator on mosfets;
Radio amplifiers on mosfets;
Portable desktop - super pocket welding power supply for precision welding + diy probe for the electrode;
Analog arbitrary waveform generators on mosfet;
Linear RF amplifier on mosfet;
Precision Pocket Induction heaters for plugs welding/soldering like here :
And so on... so basically as i'm interested in all of these stuff,for this reason i'm searching an
nor super cheap nor super expensive Mosfet which must be at least a little better on Vds and parassitic capacitance

P.S : I forgot to tell you,IRF 510 is not very good for the DIY of Metcal power supply,because of the low Vds wich is making it pretty vulnerable in that kind of system