I came across a supplier in PE that sells amongs other products acoustic board, green glue, "sorbothane" etc. Boards are 1220x2700 in 12 or 9 mm thickness. Sorbothane is 1300 width x 3mm, any length. They deliver in Pretoria but as I have a small order will perhaps have to wait till a big enough load to Pta is ordered, or pay extra for delivery. I haven't done business with them before, so obviously no affiliation. If anyone is interested please pm for the website, don't know if I'm allowed to give it here?
