Not sure if this system uses the same fluid as Citrone/Peugeot but i'd assume it does as they use the Peugeot engine.

I'm sure GSF/ECP sell the fluid but its still not cheap.

I think you can buy a re-fill kit for about £75 but i can't remember where i bought it from.

It may have been Volvo as this was the 1st car with this system fitted that i had to do a fill up on. (almost identical kit that i bought for a Citrone C8)