I bought a front elastometer yesterday for £16 from Avon Valley Cycles in Bath, UK. They have hard and soft versions. However, really they are just a bit of high density foam - easy to fashion one with a razorblade and a bit of foam I reckon. The soft version has a hole down the middle you could fashion with a heated skewer or screwdriver - the hard one for heavier riders does not.
I have a LitePro 52' replacement chainring - works fine and less messy (ie no plastic retainers) than the original. I have spare 52 and 48s.
I also got a Birdy Bargain recently - a very good condition 24 speed 2001 model for £270. They are around occasionally - usually sold by people who don't know the real value of these bikes, whcih tend to run above £500/US$700 on Ebay and such sites.
On brakes, AlixPress (Chinese exporter website working in English - reliable) - do many aftermarket spares suitable for Birdys. You can get color coded lightweight V brakes, replacement suspension, chainrings, seatposts, , brake cable microadjusters, v brake adaptors to use 20" wheels , etc. Sometimes you have to dig a little deep on their site to find all the litepro parts. My stuff was delivered to the UK in 2 weeks, postage free. I got a chainring for $15. New 18" wheels, each with 4 bearings and red in color, can't remember the price but they are good and they are still selling them.
Thanks. I had seen Avon Valley Cycles in my initial search, but it seems they don't ship outside of the UK (I'm in Canada). But thanks for the info about construction. Any chance you have a way to measure the outside diameter and length?