I managed to get a couple of Webco's for CR125 from ebay. One in Sydney for $75 including postage and one from the States which cost AU$95 landed. DG's and FMF porcy's are a little different in price though. I have found it easier to buy complete running bikes with them fitted for better prices. Replace the heads with standard ones, keep the fancy ones, sell the bikes, heads are cheap. They're out there if you are patient.
K