It seems that it was more common for anti-slavery boycotters to seek alternative products that were generally not produced by slave labor, rather than seeking the same products that were typically produced by slave labor, but from specific producers that relied on free labor.

For example, in the case of Britain before the abolition of slavery, those who boycotted slave-produced sugar (e.g. Percy Bysshe Shelley) did not, as far as I know, seek to acquire sugar from free-labor sugar plantations, but rather often drank green tea, which they regarded as not requiring sweetening.

Another, more American example is the case of the Fruitlands, a transcendentalist commune. They did not acquire free-labor produced cotton, but rather wore linen clothing instead. (Unfortunately, linen is a fabric which breathes very well and will generally keep you cool in hot climates -- but do nothing to keep you warm in cold climates, and the Fruitlands were in chilly Massachusetts.)