996.2 Anti-roll bar dust cover - replacement?

[mark seeker]

I took my 996.2 GT3 for an MOT at the weekend, it passed but had an advisory for:

Near front lower anti-roll bar Linkage ball joint dust cover deteriorated, but preventing ingress of dirt.

The car is due a service next month, I obviously want to get this replaced but just wondered what the cost should be (always nice to know in advance to make sure I'm not getting ripped off).

Thanks in advance