I love my Long Perng 7mm - 21mm zoom eyepiece. Bought it from Andrews Communications in Sydney. They also make an 8mm - 24mm which costs a bit more. Talk to Luke at the shop and he'll tell you that they're just as good as William Optics.
Many nights I just pop in the zoom and head out with a 2.5x barlow and a 25mm plossl and that will do the job nicely. I highly recommend this zoom eyepiece to you.
Glob.
PS, here's the link to the shop
http://www.andrewscom.com.au/