if you enlarge onto direct positive paper, you will have ... a negative print as your cyanotype ..
don't bother with lith film or xray film &c ...

paper negatives have been used to make photographic prints since ... 1839
i would make regular b/w print, then make a contact print of THAT to get a negative ..
make sure you use photo paper without printing on the back .. or hand coat your own thin paper,
or use slavich paper .. i believe they still make single weight paper ...
then take parafin and an iron wax the paper negative .. both sides.
don't use too much wax and smooth it with iron and rub with a paper towel to dry it
( both sides front and back )
you should notice the paper is sort of see through ...

coat your cyanotype paper, put your waxed paper negative on it, and leave it in the sun ..

i have done this with both hand coated paper negatives as my paper negative
as well as a xerox which is much thinner paper. they both worked OK ...

it was around new years and the exposures were extremely long ...

http://nanianphoto.com/blog/?p=374