My preferred supplier is
http://www.bulletsdirect.com/
But... it may be cheaper to order a Lee 2-cavity mold to use in this interim period, as long as you're willing to deal with the lower quality.
You could get the .410 Lee 2 cavity 195 gr SWC for about $18-20. (There's also a 210 gr Tumble-Lube version.)
I have a 195 SWC mold that I bought for other purposes, and for my brother to use for his .41 Mag. It drops bullets at .412", when cast with an alloy of WW +2% Tin (and an ounce of magnum shot, for a trace of arsenic). Even with something like Isotope alloy, it should drops bullets that are still .411" or larger. Only with an alloy close to pure lead, would it start dropping bullets at the advertised .410" diameter.
Lee molds are crap, but they do get the job done.