"Optional machines to work with"

Solution 1:

To start and finish with,

• Optional machines to work with

is not an English sentence.

It is an English Noun Phrase, with an undetermined head noun machines, modified by an ambiguous modal adjective optional -- optionality of the work or the machines? -- and a subjectless relative infinitive clause to work with.

There are a lot of ambiguities and missing referents in this noun phrase that must be resolved by the (hopefully well-trained) reader. With that many problems already, I don't think the risk of additional outrage over a stranded preposition is even worth considering.

Executive Summary: Start over.

Solution 2:

Your description of the machines made a lot more sense than the particular noun-phrase you use.

With the limited information you've given, I'd suggest "Alternative machines/tools available".