where can i buy a NTP12N50 power transistor?

I am building a solid state tesla coil and i cant find the NTP12N50 or NTP12N40 transistors, does anybody know where i can get some? here is the website i am using to build it http://www.angelfire.com/electronic/cwillis/fetcoil2.html.

You should be able to use a IRF740.

Jamesco Electronics has the IRF740 which they show as equivalent for $0.65.  Looking at the circuit I think that Jamesco is right they would be equivalent for this project.

The link you attached with the circuit suggested getting samples from On Electronics.

IRF740 - N chan, Vdss = 400V, Id(max) = 10 A, Rsd(on) = 0.48 - 0.55 ohms
NTP12N50 - N chan, Vdss = 500V, Id(max) = 12 A, Rsd(on) = .5 ohms

Jamesco link:

On Semiconductor (maker of NTP12N50) link:
Jimmy Proton (author)  Doug Paradis6 years ago
well i didnt see anything for samples or buying on On Semiconductor.
That pretty much covers it.