Replacement bulb for N Gauge Bachmann Santa Fe F7A Warbonnet

[drt7uk]

Hi folks,
 

Unfortunately I've broken the light in my N Gauge Bachmann Santa Fe F7A Warbonnet - part 10015, see 1st image below. 

I'm trying to find a replacement, and unfortunately Bachmann are all sold out of the original bulb (https://estore.bachmanntrains.com/index.php?main_page=product_info&cPath=70_108&products_id=224&zenid=2kddspucr9qfrlnrhdg6j7uem7).

I tried using a 12v 1.8mm LED, but I didn't use a resistor, so it flickered and didn't work (see 2nd image below)

So I've tried to purchase both an 1.8mm LED with a resistor, and a incandescent bulb 3mm x 9mm (see both below, 3rd image). I'm concerned there is not going to be enough space in the loco for either!

Has anyone else had to replace their light bulb, and if so, where did you find one? Did using an LED with a resistor work?

Thanks a lot,

David