How to Mount Circular (138mm?) Tiffen Filters on CP-16R

[Alain Lumina]

HI,

 

I lucked onto some pro Tifen filters-- low contrast 4.5 , soften net, for nearly free, and

they are in a 138mm round format with no threads.

 

I have a CP-16R film cam with a Canon zoom lens with 72mm threads, assume I'll have to buy

some kind of filter holder or matte box ( I can't afford $1500 matteboxes I'm afraid)

to hold the filters.

 

Any ideas? Gafffer's tape is fun but doesn't look so good.

 

Thanks!