mark - they are for the tk23, but i dont know if there will be problem using them with the mt45 , im not femiliar enough with master. any way, there is only one film in this format - the hp5+ (u can find it in b&h in ny) , which any way one of my fave films..lol.
u also can call the b&h and ask them because they do have the linhofs.
but then - u know, why should u, cause u have much better choice of film in the 4x5. if u want the 2/3 proportion u can crop - say 8x12 instead of 9x12.
what u also can have for the master is the slide-roll-film-holder from linhof, it is less expenssive as well than the roll-holder, which u dont need if u focus and work on the groundglass.