Replacing tired window netting?

[bmonday]

The zippered mesh in then panels that cover my Bedouin RTT's windows and doors is getting quite old and fragile. If anything bumps against it now it tears in a heartbeat.

How would I go about replacing it? Do tent manufacturer normally have replacement panels available that can be sewed in? Or do I need to take my tent to some kind of specialist and have it done?

Thanks in advance
BMonday