replacement elastic bands for Hvidt chairs  

Pirelli
Pirelli rubber webbing is widely available, as are the metal clips to put on the ends

how about
the round slender springs that are rubber coated (red)? any source for those?

Those
Those, I don't know where to get..

Re:Glass
I think the rubber coated springs can be had from Fagas straps in Denmark. Also the flat rubber straps too. It should be googleable (inventing words aren't I).

There are
There of several people selling it on eBay UK, but none in the US apparently.
http://cgi.ebay.co.uk/DIY-UPHOLSTERY-SUPPLIES-PIRELLI-RUBBER-WEBBING-ERC...

... just to help you on your...
... just to help you on your way 🙂
http://www.fagas.com

thanks so much
this will clearly get me started. The expersprings on the Fagas website seem as though they will fit the bill.

To Confirm on M andersen
Hi The springs you need are called xperweb and FAGAS are THE supplier you need.
Ever so simple to fit as the spring comes on a roll and you cut the required length of. A small piece of thread simply fits into the ends you have cut and there you have it!
Simon
Danish homestore

THANKS!
to all! my hans olsen rocker will rock again!