There were about half-a-dozen missionaries on Harris at the time of each of the 1881-1901 censuses but I have extracted these four because each specified that he was a ‘West Coast Missionary’.
I have yet to learn anything about the West Coast Mission (other than that there are very few other members to be found elsewhere in the census records).
Donald Campbell, 40, Strond, b. Islay
Malcolm McLeod, 37, 5 Marig, b. Lewis
Donald Matheson, 48, Strond, b. Skye
Edward Mackay, 39, No 32 Scarp, b. Easedale, Argyleshire
It appears that the West Coast Mission came under the auspices of the Glasgow Reformatory Institution (at least, they published reports from it), a reference to which appears here: http://canmore.rcahms.gov.uk/en/site/161952/details/glasgow+211+duke+street+house+of+refuge+boys/ and which someone attempted to burn down in 1861 according to the National Archives of Scotland.