Log in to the Second Life Marketplace website.  

Then, locate the page of the product you want to update.

You'll see that there's a banner at the top pf the page that says "You purchased this item on.." followed by the date you purchased the item.

Click on that date.

You will be shown  a list of all the items you have bought on that day, including those from the Exosphere store.

Select "Redeliver item" to get the latest version of any of your listed itens.  It will be delivered straight to your inventory.

This can also be useful to retrieve Exosphere products if you have acidentally deleted the original item you purchased.