[MartinP]

The ORIGINAL specified bulb has been discontinued but has been replaced by another with identical properties and fitting. The universal code number for this bulb is 13139

The 6604 and the 13139 are not the same fitting. There were two different versions of the bulb-holder in the V35, due to the original bulb being discontinued by Philips. There is a handy diagram and details at this link. Also note that there are a couple of different versions of 13139, with different manufacturers and very different expected service lives.

I looked on my previous supplier for Philips 13139 and they are "no longer available - last stock" on the website. This mod, by the OP, could be very useful in the future.