I couldn't find flax flour here in Brazil, so I've made with chia flour. (elanaspantry.com)
PB: Savvy Beast Treats lists organic chia flour as the first ingredient in its products. (petbusiness.com)
Typically, my suggestion for making a recipe eggless is to use a «chia egg» (1 tablespoon chia flour + 1 tablespoon lukewarm water, mixed and allowed to gel). (glutenfreeonashoestring.com)