Although clerics are the main healers in most games, they are not the only ones who can heal. Paladins, rangers, bards and druids all have access to healing spells and can use wands of healing even at first level. Even rogues have the use magic device skill that would let them use a wand of cure light wounds.
In a campaign I recently ran I had the same situation. I came up with 2 answers. The first was to have the party find a wand that cured light wounds 3/day. The second was have a npc cleric with the party. The cleric was a lower level than the rest of the party. So even though they could rely on the clerical skills for healing they had to protect the clearic from untimely harm. Most importantly with the npc cleric was to have them accept the npc as a person and not just a healing machine. This was done by tying some of the characters personal plots to the npc and giving them even more motive for keeping the cleric alive.
In a campaign I recently ran I had the same situation. I came up with 2 answers. The first was to have the party find a wand that cured light wounds 3/day. The second was have a npc cleric with the party. The cleric was a lower level than the rest of the party. So even though they could rely on the clerical skills for healing they had to protect the clearic from untimely harm. Most importantly with the npc cleric was to have them accept the npc as a person and not just a healing machine. This was done by tying some of the characters personal plots to the npc and giving them even more motive for keeping the cleric alive.