Skip-tooth chains are pretty cheap here. Under $50 as these chains were very common on US heavyweights. A cog may be a bit more tricky as it needs to be compatible with the hub, but those can be under $20.
The Copake auction site would be a great place to look for handlebars.
http://www.copakeauction.com/
Good luck with your project. Looks to be a fun one.
IAB wld you happen to know the type of bike or handlebars? These really oldies are a new breed to me. :-)