To look into the price and availability of reclaimed hardwood railway sleepers and hardwood timbers in a Country, the type required are TEAK or other tropical hardwoods would be considered which are untreated with chemicals.
The supplier should be as close to source as possible with first contact a department like the ministry of railway to get information and if they cant help then contact a main contractor who carries out maintenance work on the railway tracks.
Sometimes suppliers of railway sleepers classify the sleepers in grades of quality /length I would be more interested in the best grade ( timber has minimum shakes/cracks) and the larger the timber the better.
This project is for the research in one country which can be completed easily with a few phone calls/emails within the Country you live.
If a good source of reclaimed timber is found there may be further projects related to it .