app/views/spree/admin/products/issues/_form.html.erb
<fieldset>
<%= f.field_container :name do %>
<%= f.label :name, "Issue Name (Optional)" %>
<%= f.text_field :name, class: 'fullwidth' %>
<% end %>
<%= f.field_container :magazine_issue_id do %>
<%= f.label :magazine_issue_id, Spree.t(:product) %>
<%= f.collection_select(:magazine_issue_id, @products, :id, :name, { include_blank: true }, { class: 'select2 fullwidth' }) %>
<% end %>
</fieldset>