Could this be of any help?
The rail type is 2lb a yard. a good website is
http://www.miniaturerailwaysupply.com/
You may be able to find a bogie on e-Bay (ive seen wheelsets for a 5inch britannia, so who knows?)
Sleepers could be just be 18 x 28 square wood cut to 10 inch lengths, rails held in with nails, screws or carriagebolts with suitable square washers. since you are not running any locos on the track it should be more than safe. sleeper intervals could be maybe 10 to 15 inches (Again, beacuse it will only have to support a bogie)
Who says you even have to use sleepers? you could just use 4x8 Plywood and track laid and bolted on top (like a tramway)
The carriagebolts can be tightened using a spanner or even an airgun.
Hope this has been of any use to you.
- Jeorge