Hi Tinderbox (UK) , Rycote of Stroud Glos.Tel. 01453759338 can supply a very effective " windjammer" fur approx 10mm thick at a reasonable price.
How about blanking off the first row of microphone holes, as seen on your pic, with tape and then fixing fur. This should keep the usb cover unobstructed and although not being an expert I doubt if it would affect your sound pick-up very much.
I have a Sony TG3E have (carefully) stuck fur with glue avoiding mic.holes. Use a glue that will not damage your camera or try stick on velcro to both surfaces.
This has worked for me.....why manufacturers have not dealt with this issue beats me as it was the first thing I noticed on playing back clips taken in even light winds.
Give Rycote a call and explain your needs. they were very helpful to me, they have a website
www.rycote.com You only require a small amount of windjammer fur...they supplied me with 1ft. square of material which gives a few trial cuts and plenty spare for re-covering at later dates.
Yes it does look like a Mohican but does the job as there seems no alternative.
Regards , tg3euser.