How many neg carriers does one really need?

What's really hard is getting D5 carriers for previously common films that 'no one' uses anymore. I need to find some for 127 4x4, 126 Instamatic, 110 Instamatic. If I ever see them people want more than today's cost for an entire enlarger !

I made some myself for odd sizes - using matt board and a spare anti newton glass from an old Durst enlarger - for instance for 24 x 66 mm - the format of my Noblex.