Hiding bulbs behind the dash doesn't seem like a very elegant solution. People on Ebay sell 25W and 50W ballast resistors to help with relay loads when fitting LED bulbs. I'll either buy new indicators or fit a fixed rate flasher relay off another vehicle.

I have led indicators at the rear and got my resistors from svc, they are not like an ordinary resistor as in your pic they are also mounted on a small piece of aluminium to disipate the heat

I think they were about £8 each but i did buy all my lights in one go from them so i may have got them a little cheaper