You have to go through Costco directly they have the link online with different stock. My local costcos didnāt stock anything lower than an H6 and wouldnāt order it for me. They told me to go through the site, but the site wouldnāt allow me to order it anyway. Which is half the reason I went...
I just did this with a Walmart Everstart H4 AGM. Rockauto was 180 with shipping for an H3 AGM, and Costco didnāt stock and couldnāt order any Interstate H3 AGMs or H4 AGMs. However itās a simple upgrade with just an oscillating tool, and for $189 at Walmart with a 4 year warranty itās hard to beat.