Late-model B-17F nose cone (1/48)

Hello everyone,

I'm just starting work on a B-17F, converting the Monogram 1/48 G kit, and am weighing my options on dealing with the nose cone. The Memphis Belle kit's is custom, with two .50s, but for my aircraft I need a single .50 mounting in the center. The Koster "Nose Job" set is long gone, it seems, so I'm trying to figure out what the best way forward is. I'm considering trying to vacuum-form one, making a plug based on the shape of the Belle cone, but I've never done it before and am a little intimidated. Any advice would be much appreciated!