hi colin

would paper negatives work for you ?
they are orthochromatic, and slow and like olde filme .. sort of.
since you are shooting large format its easy ... ( and maybe already in your darkroom ).

you could also coat your own ( i like doing that these days ) with liquid emulsion
and regular paper, or glass. the only thing about the glass is you need plate holders
and it takes practice coating it ... paper is a piece of cake ...

good luck !