Do you just need timefield and not the complete datetime xtype ?
Use the dialog converter tool to convert your dialog field.
download and install DCT from the link below.
This should be the resourceType in touch UI
With Touch UI - you can write a custom resource type to meet you needs (if the ootb ones do not meet your needs) -- see this where we use a Color picker as an example -- Adobe Experience Manager Help | Creating a custom Experience Manager sling:resourceType for Touch UI
You can use the type property of the DatePicker Touch UI component to "time" to only use hours and minutes.
But, depending on what your goal you might run into issues - as this stores the property as a date and not a string, as the timefield does. This could cause issues if your trying to use both dialogs while moving authors over to touch ui. Then you would need to follow Scott's advice and create a custom Touch UI Granite Component.