Look for Chosen Foods avocado oil mayo. The label says zero carbs, but with eggs and honey in it, it's probably .5g per tablespoon. Costco sells it online for $7.99 for 24 oz., and that would be cheaper in the store. Otherwise, you can find it for around $7 for 12 oz.

Primal Kitchen is $8.50 for 12 oz., so a little more if you buy it at a regular supermarket, with the upside of no added sweetener.