Well, good luck. Type 55 P/N is no longer made. The price of new old stock has gone through the roof.
However, the news is not all bad.
Polaroid 405 and 550 holders work with the appropriate Fuji instant print material.
If you are adventurous, you can try Kodak Readyloads (also discontinued) and Fuji QuickLoads in a Polaroid 545 holder. Numerous sources on the web say this works. I have all 3 but haven't used the combinations yet.
Anscojohn: I have a 405, 545 and 550 holder. They all work on my 1953 Pacemaker Speed Graphic.