When Unitol was discontinued (as was Johnson's of Hendon) and I had to swap, it more or less coincided with my move to medium format. Having less worries about grain I went to Rodinal as a one shot liquid like Unitol, but different insofar as the formula was published. So long as the raw chemicals are made I should be able to continue.
And as Lindsay said, there are alternatives using store cupboard ingredients as the TV chefs say, even if the store cupboard for some is located under the kitchen sink.