Do they want all slicers or would take a combination of slicers and picklers? In many situations, customers prefer the smaller pickler types for salads and other fresh uses. Lots of good picklers available. For a longer setting period choose a monoecious.

A nice slicer on a more restricted vine is 'Fanfare'. Would require some repeat sowing as the sets can be kind of concentrated.

I have found Lemon cucumbers to sell well to repeat customers, even as a "specialty" type cuke. Produce customers often buy what they know, so offering free samples helps. Lemon cukes are sweet, never bitter. Since they are round, even the small ones toward the end of the season can be packaged together as bite sized cucumbers for salads, etc. I harvest them right after all of the spines turn black.

My favorite slicer is the Amira or Babylon, both a sweet never bitter,no need to peal cucumber. These are great early cucumbers and for a late season cuke I look at marketmore cuke.

I raise pickling cucumbers and sell wholesale as well as retail. MY favorite pickling cukes are Regal from Harris Seeds. Cross Country from Stokes and Eureka which is available from several seed companies. Since I hand pick my cucumbers it is important that the cucumbers grow over the entire summer. My favorite slicing cucumber is General Lee. My market wants a smaller more slender slicer . General Lee is perfect for my market. Good Luck.
Linda