Compounded low dose naltrexone? Costco Specialty Pharmacy?

I was looking to price out low dose naltrexone (4.5-6mg). Currently chains and Costco only carry 50mg versions with the lower dose needing to be compounded. I was wondering if anyone had experience ordering it through Costco? It seems they have a specialty pharmacy company: https://www.costcohealthsolutions.com/pages/Members_SpecialtyServices.aspx