Yes, there are options, but ultimately there are some bottleneck using PowerBI. You can get the Service Request Item’s custom fields if you set a Service Item =/includes Service Item Name (need to type it as it doesn't auto recognize and is case sensitive).

The bottleneck is that you can have one scheduled export per module, in this case, Tickets. If you export it with one service request item, then you've consumed the tickets module data export and can't make another one, so you would need to include all conditions in one single export for it to work. On top of that, if you filter by a list of Service Requests Item(s), you leave out Incidents. To do both, you’ll need to set up an AND/OR with an advanced filter and create one group for all Service Request items and another group for Incidents. Lastly, the export only supports up to 70 fields and you may quickly run out of fields when you bring the basic properties + all the specific form fields from the SR if you have a lot of custom fields across multiple service request items - most do. 

Without filters, you will not see the custom fields on service items. 

After adding filter(s), you can see the custom fields for Apple iMac are now selectable (lower left).