They didn't stop producing it - they only make them according to demand. I shoot the Hornady 180grn SSP Interlock 3505 bullet and the 180grn Speer Hot Cor 2435 out of one of my Redhawks, both are "seasonal" or "by demand" production bullets. They're a specialty bullet, not really high demand, so they don't make them very often. Midway discontinued them, but they'll pop up again next year when Hornady releases more.
I ordered 300 of the Hornady's a few weeks ago from a shop in Indiana, they said they had 1200 more left - I was tempted to buy all of them at the time.
Place orders where you can find them available for backorder, that drives Hornady and Speer to produce them.