The large frame Flattops in .41 Magnum were a distributor exclusive from Williams Shooters Supply, and were the same gun as the 6 1/2" 50th anniversary .44 Magnum Flattop, but in .41 Magnum, and with the 2nd barrel length available in 4 5/8". They had no anniversary markings of any sort obviously though. They are long out of production as of this time. The model 0405 and 0406 are standard large frame Blackhawks and are available to dealers from any distributor that carries the Ruger line. I don't stock them, but when somebody has me order one in my price on them is $485 shipped. They can be bought used in the low 4 range.
Williams Shooters Supply is in Quincy Illinois, and is a very large national distributor who sells to dealers only. They are a full line Ruger supplier, and the owner is one of the many helpful forum members here.
They have 10 of their own distributor exclusive firearms at this time, 9 of which are Rugers, 6 of those being revolvers