The above Narva 47734 bulbs are NOT the same as the GM ECC (Electronic Climate Control) illumination bulbs.
The correct bulbs have a 1/2" (~12.7mm) diameter base, not 10mm, and the contacts are not in line with the bayonet tangs, but at 90°.
I spoke to Narva and they assured me that they do not have the correct GM bulbs.
The GM bulbs go by 3 different part numbers and these may simply be a case of with the green "condoms" or without. The prices were the same on each part number.
92140514, 92140515 & 92142572, all having the same disgusting price of $12.70 each plus tax.
Apparently these are also used in some Volvo ECCs and go by the Volvo part number 9472403, with an even more disgusting price of $20 each.
However, I have ordered a qty of 10 x-USA and am waiting for them to arrive. They appear to be identical to the GM bulb and if they are correct, I'll have 10 for less than au$30 landed.
I'll update this thread when the postman comes.