Crankshaft gear - no longer available

[heavend]

I was replacing a cambelt and oil seals the other day. It's a job that involves pulling off the crankshaft gear off. Normally this isn't too hard, but this one posed a problem - it cracked!
Volvo no longer carry this part. There is a Renault part number 7700100776 - which is the gear from a 1.9DCI RENAULT CLIO II, MEGANE, SCENIC or LAGUNA, available readily on eBay. It will need machining to reduce it's height and a new keyway cut before it will go onto the Volvo. It's not a big job and I way preferred this to getting one from a wreckers...
Does anyone else know of these gears cracking? Is this why there's no original gears left?

[POE]

I came across this problem as changing oil seal and was extremely tight so I left it alone 'so maybe its just the tight fit that poses the problem and seizes in place due to age