Calor discontinuing Propane 3.9

My Trident takes two Calor Propane 3.9K and they fit very tightly in their cupboard, but Calor have just announced they are discontinuing refilling 3.9s from 1st February 2023! The only alternative I can find that will fit in the Trident cabinet are SOME Flogas 3.9kg. Apparently Flogas 3.9kg cylinders vary in size! Not all are 240mm x 340mm - the same as the Calor ones, and the Flogas ones that are not that size will not fit in my Trident. How common are these wrong sizes? I feel a disaster coming on. Help! What are the best options?

Some ideas in thread already running.

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Very many thanks, Ploughlin. I'll follow that thread.