Here is a post in a Taiwanese bike forum showing how to modify Strida 5.0 with the new upgrade parts, e.g. the 2nd generation alloy freewheel, etc.
http://www.mobile01.com/topicdetail.php?f=317&t=1630057
It doesn’t matter if you don’t understand the Chinese text. Just click on the links to see the photos and guess what the poster says. 
Interesting. Which model has those new release buttons for the handlebars? My new LX does not have them.
Google translate works on it. But then you STILL have to wonder what he’s talking about cause the translator works word for word only so it might not make as much sense. else it’s a pretty thorough article. We don’t see these metal freewheels and 18 inch fenders for sale at all yet in north america.
For Ed:
We do have the new aluminum rear pulley/freewheel available in North America!
I bought one for $60 from AreaWare in March, after the OEM plastic pulley wore out in less than 500Km of Vancouver’s wet winter.
Here is a picture of the sad plastic pulley, and the new aluminum one I have. So far (3 months, 300km), it’s been great.
The plastic pulley cogging got so bad, it damaged the drive belt reinforcing: which then jammed up between the snubber and the new aluminum pulley. Once I figured that out, I changed the belt as well, and all is fine.
That plastic pulley should never have been fitted to a Strida…
Even the older Strida 3 uses a sturdy zinc pulley cast in with the brake drum, I think.
cheers,
Minkair.
Wow Mink that’s some pretty serious wearing there! I’m in Toronto so we don’t have the same wetness so it’s not that bad. after a year of commuting so far there’s no wear at all. But I’d still like the metal cog eventually.
I’ll probably be ordering that cog once mine starts to wear but so far it’s good. It’ll stay that way as long as you are able to keep it clean from dirt which is giving it that sandpaper effect on the cog and belt. And it’s especially hard when it’s wet which chains and belts become dirt magnets. Usually when i’m going through a long gravel path and the belt gets dusty i’ll hose it down and let it dry after.
60 bucks? Wow. Did not know that’s how much they’re going for. I don’t want to make you feel bad, but I got my alloy pulley for free from Strida Europe when I complained about my worn plastic pulley (very similar amount of wear to yours). From their reaction, I got the impression that this is a well known problem.
I recently this week received my metal freewheel. But the beauty is I wasn’t specifically ordering it but was ordering the 18 inch wheelset, which comes with the alloy freewheel already attached. After finding that out I thought the 18 inch wheelset had some pretty good value in it for around $200usd after taxes. What’s amazing in this is that after the cost of the parts the wheel and spokes and hubs are pretty cheap ($60 freewheel, $80 for kojaks, = $60 left over which is the rim, spokes and hub and new disks for the brakes). In the end you couldn’t get a better deal with this combo.
Only problem I had was trying to carefully pry off the belt because I didn’t have the tools for the bottom bracket but it was easy looking at the instructions they included. And some minor tuning on the disk brakes cause the disk was newer and the pads touch it because I keep a very low tolerance with my disk to pad.
Now to wait for my fenders, they said it’ll be in by late august to north america! 
It’s been two weeks since i’ve used the metal freewheel and all I can say is… this part should have been standard with the entire bike! For the entire 2 weeks my belt hasn’t even skipped once with the usual force that i’m applying when on the uphills and standing starts. Usually I get one belt skip every other day but it was just weird when I put down the pedal the bike just went! It’s pretty much a necessary upgrade for everyone that owns a strida I think if they like doing hill climbs alot with their bike.