1) Try setting up an account with IRCTC. But wouldn't work if you do not have a Indian Mobile Number.
2) Try booking at the PRS Counter.
3) Try to contact a registered IRCTC Agent or any other businessman involved in this business.
4) Try to avail Foreign Tourist Quota (If available for the particular train/class of travel/journey leg) once you arrive at India...
more... by visiting specific counters at selected stations by showing your passport in original.
5) Try to register via Cleartrip. There is a slight tweak discussed at Indiamike by which you can bypass the need of an Indian Mobile Number for registering at Cleartrip and IRCTC.
Thanks.