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Some barrel lenses can be mounted directly in shutters, like G-Clarons and some enlarging lenses, while the others are nearly impossible (Zeiss Jena Apo-Germinar W for example), because the lenses are mounted directly in the barrel. Those barrel lenses that have cells that easily go into shutters have basically just an iris mount in place of a complete shutter.

The cheapest way might very well be for you to find a strong neutral density (gray) filter for your lens so at an aperture of f/22 or smaller you can expose for a few seconds in broad daylight with the aid of a black hat or black paint can cap, or an empty small paint can that is painted black: anything you can cover your lens with without touching it.

If you intend to use paper negatives, you might just as well get away without a shutter.

Using paper developer for your film will also reduce your film speed, which can help.

After these come Packard shutters.

Or you can just take out the shutter from an old battered Pentacon Six, put it in a housing and use it right behind your lens.

There are many possibilities but at the end, it's worth putting aside for a lens in a shutter in your standard focal length if you're certain LF is for you.