Agfa didn't sell sheet film after all. And if you were using Fortepan 200/Bergger BRF 200 - would you really consider APX 100 a close replacement?
I don't know where you got this bit of ill-informed information, but I have used Agfa sheet film in 4x5 and 8x10 for years, and stiil have some. Not only APX-100, but also 8x10 color transparency. I believe APX-400 was also available in sheet film. By proper exposure and development you can get top-notch results from the now discontinued Agfa APX-100 in sheet film sizes. At one time Agfa also made some other "specialty" sheet films.