all depends on how much of it you want. An option is PE chopping boards from a kitchen supplies shop. Reasonably cheap and various sizes available. It's not HDPE but is more than adequate for most situations.
I got mine from EBAY - (1x WHITE HACCP Plastic Cutting / Chopping Board (thick) (eBay item 250549343410 end time 11-Nov-10 13:02:08 AEDST) : Business).
510mm x 380mm x 19mm. $26 pick up from Sydney. Various sizes/colours available.