You mention that a cousin could bring you supplies from Canada. If so you might try some of Ilford's direct positive paper as well. It is available in 4x5 size. It is very slow so portraits could be tricky and some testing to find the right exposure for your equipment may be necessary. You would develop and fix as with regular photographic paper.
I see nothing wrong with 4x5 prints and make 4x5 platinum/palladium contact prints. In my opinion print size should be determined by how far from the print the viewers would be. Consider that books generally have small prints. If as suggested scanning is an option but you still want to print with "traditional" photographic paper you can scan and enlarge a negative on to transparent media such as the Pictorico transparent film and contact print from that.