You will be able to purchase a replacement four-headed infrared control cable from the Sling Media's Online Store. Use the following link to complete the order:
Found that if I positioned the units to be controlled within the field of my 2-way IR Blaster I am able to control the units
Also found out that my SKY+HD BOX, Amstrad DRX890 looks like it is controlled through the cables as it is not in front of the IR blaster but I am still controlling it. Or the range of the blaster is wider than I think.
Also, thanks for the link, unfortunately I am in the UK and the replacement shop only ships to the US. Maybe Sling should open a European Retail Branch?