I made a cheap heater for my old Ideal 45 and the newer RCBS sizer. Went to the scrap dealer and found a beautiful piece of 1/4 " aluminum, 12 inches X 12 inches. Cost : $4
Hacksawed a 4 inch strip, then cut a 4 inch square off of that. Drilled, countersunk and tapped for three 8/32 screws ( about a dime each,)and ended up with an 8 inch X 4 inch rectangle, half of which is double thickness (1/2 ".) Trued up all of the edges and rounded the corners on the beltsander so that everything looked good.
I drilled mounting holes for both sizers through the 1/2 inch end, which line up with the holes already in my bench. The 4 X 4 piece goes down on the bench, and the long end sticks straight back, with a 1/4" space between it and the bench. I put an old travel iron (free from my older sister) on its lowest setting on the back plate, and since the plate doesn't rest on the bench, the heat moves straight to the sizer. After about 10 - 15 minutes I take the iron off, and only put it back sporadically depending on how long I size. Even though I don't use a really hard lube, a little bit of heat makes even the soft ones flow like butter.
Total cost, about $4.50. Good deal.