If you do a search you may be able to find ERCO's number on some forums.
He is still a wholesale parts supplier to the trade.
There are however, much better springs available these days.
Either PAC or PSI Beehives with ovate wire are very good,
CB650s are good too (but a little heavy for mild combos), as are JPM duals with ovate wire.
where's good to buy these for our VW's? in the UK.... i'd love to run beehives