Dear Robert,
A great deal depends on whether you are shooting mono or colour, surely.
In mono you can get film for almost anything -- it's just a question of price -- and it's a lot easier than it used to be to have film cut to size: minimum order quantities are surprisingly small even for weird sizes like 12x15 inch, as little as 50-100 sheets from Bergger for example.
The only way I use my 4x5 inch cameras nowadays is for colour transparency or (in monochrome) with roll-film (6x7, 6x9, 6x12) because I much prefer the quality that I get from 5x7 inch or (as I have noted elsewhere) a 3x enlargement from 56x72mm to give me a whole-plate.
Cheers,
Roger (
www.rogerandfrances.com)