I have a Form that includes a lookup on a field; Part Number.  The lookup is used to provide an initial list and is then used to populate a second field; Description. Refer to pic.

This works fine in a web browser.  A double click is required to show the lookup list in the first field.

However, I require the same Form for an iPad.  The iPad does not have a double-click and when the field is selected, the initial list will not show.  I can start typing a number in this field and a list of available numbers will appear but not a complete list.  I have to enter at least the first character for the list to appear.

Is there a script that will show the list when I click once in this field?

Please bear in mind that there are three such lookup fields on this form, which have to be individually focused.

Your help would be appreciated.