I'm posting this in case it is helpful to anyone else.
I started riding again in January after a long absence. I was thinking about roadside assistance, considering NRMA membership for the car a no-brainer. However, adding the bike to my NRMA membership would apparently have cost an $120 per year. I looked at National Motorcycle Alliance, but was unsure, because I wasn't familiar with them. It did seem like a good idea though, for $50 per year you get membership of a representative body, which includes roadside assistance, so I joined.
I had my first need for assistance this week, with the electrical fault referred to in a separate thread. I found NMA excellent. I called during afternoon peak hour and was advised by the operator that it might take a while to get a technician to me, but she could organise a tow truck immediately. The tow truck operator arrived within 20 minutes and was extremely helpful, so all in all a very positive experience.