Does anyone know a good online source for a 40t chainring, preferably for a single chainring application (i.e. with no shifting ramps/pins)? I will also need a couple of chainguards to work with it.
The plan is to install the chainring in the outer position on the spider, the inner chainguard in the inner position, and the outer chainguard on the outside of the chainring along with spacers between them.
And I cannot seem to find chainring bolts long enough to fit the chainring, the two chainguards, the spider tabs and the spacers needed between the chainring and the outer chainguard.

TA makes 40 tooth rings in 110, 130, and 135 mm bcd. I would guess Stronglight and Sugino do as well. You can find places in Europe or US selling all three of these brands. Cheaper to order from Europe.

http://www.peterwhitecycles.com/chainrings.asp

You can always try a BMX ring... available in 110bcd with no ramps or pins. Probably a lot cheaper than any of the "regular" road rings.

Thanks for the tip. I will see what I can find, hopefully on the lightweight side.

Found a quite lightweight BMX chainring in 40t:
http://www.porkchopbmx.com/Chop-Saw-I-C ... -BLACK.htm

Had a hard time finding a 40t chairing guard, but Erin from BBG told me I can safely use his 39t guards with a 40t chainring.

The last missing piece of the puzzle - where can I find extra long [alloy] chainring bolts? Based on my calculations they need to be 7mm longer than the standard ones, to accommodate the 3mm spacers and the extra 2mm chainguard.

try mtb bolts - the ones used for fitting a bashring. They are pretty wide.

The BBG guards are quite thin, so you might not quite be as fat as you think.

JB importers carries the Origin brand also sold under the Tuff Neck Pro Neck brands. These have a 110mm and 130mm bolt holes. This eliminates the bolt problem since you can use one set for the guard and the other set for the spider. They are available in 1/8 and 3/32 thickness. $9.99 wholesale. http://www.flickr.com/photos/63373992@N07/7122647301/