How to get a "product picker" for a custom SKU field

I have added a custom field to the SKU class, and I would like the interface to display a drop-down list of all of the products/skus within the site.

I have tried setting the following properties on the field, but I only get one result (even though AllChildren on the specified node shows the results I desire within the macro selector popup), and it just shows the default .ToString() implementation of the node instead of the DocumentName:

Data Source:  Macro Expression:  Documents["/Alias"].AllChildren
Text Format:  {% DocumentName %}
Value Format:  {% NodeSKUID %}

How can I get this drop-down list to populate correctly?

Also, is there another way to get all products from a macro without having to specify a node? I tried setting the data source to CMS.Ecommerce.SKUInfoProvider.GetSKUs(CurrentSite.SiteID), but macros seem to be limited to a specific set of commands/properties.