I know Bradley Buttram has RC Black Minorca large fowl,but I think he is a small breeder that doesn't have many for sale usually,but for the patient serious breeder,he is a possible source. Self Blue or Pearl Grey or Lavender Minorcas are known over seas.I read that the late C.S.Th Van Gink (Poultry Artist and writer) knew of them in the 1930's in Belgium and wrote of them in the 1950's. I currently have a small mating of S.C.Lavender Minorca large fowl,a product of ten years work backcrossing to large Black Minorcas. Lavender Minorcas are not in the APA standard.I wanted to get large lavender bird with good tail length and wide feather qualities,not all that easy with the lavender gene in the US. 
Most of the hatchery Minorcas are small and lay small eggs.Regardless of where your Minorcas are from,you can make  selections toward large sized birds in the breeding pens and then cull the eggs before you set them in the incubator by yearly raising your minumum standard on egg size and color.You want the eggs white,good shelled and  extra large in size ultimately. It is an ongoing process that takes several years to see results,but they will come if you are steadfast.