These are sites and companies that I have used and personally recommend:
Abes Audio (Australia) – HERE
Hardy Audio (Australia) – HERE
And sites and companies that others have recommended to me:
RadioCommercials.com.au (Australia) – HERE
Radio Copywriters By Earl Pilkington
Home of RADIO COPY PASTE magazine – Plus: E-Books, Resources and Tools for those of us who also work in Radio Sales, Promotions and On-Air.