It will be nearly impossible to get hold of a volvo ballast. Best chance is to either find a complete headlight unit, or alternatively, look for some BMW ballasts made by Hella which are identical to the volvo, with the exception of the wiring connetor and the rubber cover. You could possibly get one and try to make a good one out of yours and the BMW one. Have a look here:
https://www.ebay.co.uk/itm/BMW-X5-E5...Condition=3000
I have never tried it, but it might worth a try