The permissions prohibit me distributing a modified esp, but the mod author has provided instructions for adding the tent to other merchants.
Boot up the construction set with the morroblivion esm, with the travel tent mod active.
Simply find the LTTCampingTopic, and add morrowind npcs to the list of conditions for both the "I have a tent for sale" and "You already have a tent" responses. I did this by duplicating the last merchant GetIsID condition, and changing the duplicate to the ID of a Morrowind merchant.
I've tested it myself and everything worked perfectly.
I recommend non Dunmer merchants, since the dialogue for buying the tent lacks the general jerkishness of Morrowind Dunmer.