IR Filters greater than 82mm can be hard to find. Over the years I have had 95mm, 105mm and 115mm filters fabricated by the Howard Glass Company Optics Shop in Worcesteer, MA. My contact is Jason at 1-508-753-8146. They have access to Schott Glass in a wide variety of filters including BG38 (color correction CC1 - a cyan filter), OC590, RG610, RG665, RG715, RG830, RG850 and RG1000. Since they do not stock filter rings, I have had to send them an old filter of the appropriate size. KEH.com and E-bay can be useful sources for old filters in large sizes. It is a small custom shop so expect slow service and high prices.