When I used to co-wash I used Avalon Organics Lavender Conditioner. I liked it - but I realized that water rinsing was sufficient enough for my strands. But you got me thinking about using it again. Maybe I'll dilute it some like others suggested. Here are the ingredients:
Certified organic lavandula angustifolia (lavender), calendula officinalis (calendula) and lonicera caprifolium (honeysuckle) flower extracts (aqueous)(1), certified organic helianthus annuus (sunflower) oil(1), cetyl alcohol, stearyl alcohol, stearic acid, soyamidopropalkonium chloride, cetrimonium chloride, cyclopentasiloxane, emulsifying wax, beta-glucan (oat), certified organic orbignya oleifera (babassu) seed oil(2), panthenol (pro-vitamin B5), bisabolol (chamomile), arginine (amino acid), babassuamadopropalkonium chloride, ethylhexylglycerin, sodium chloride, tocopherol (vitamin E), and certified organic lavandula angustifolia (lavender) oil(3).