I bought an Enfield in Katmandu from a traveller, they're more difficult to come by there as are the parts. I was lucky, I bought from a German couple who just had a spill and the girlfriend put down her foot and said no more. Otherwise I would have had to skip riding in Nepal and wait until I got to India.
The riding in Nepal is amazing! Undescribable! I had a blast riding up to the friendship bridge that connects Nepal to Tibet.
To be sure that you get an Enfield I recommend you buy in Delhi. Check out Mukesh Motors in Karol Bagh.
When you get to the Nepalese border, tell them you're just going for a few days so that you don't have to pay a lot or limit their temptation for baksheeh. I wasn't even stopped on the way out. I parked in India and walked back to get my passport stamped.
Buy insurance, very easy to do and for a year it cost me less than $8. It's about the only thing that Indian police will check for (helmets maybe...) and gives them an opportunity to put the squeeze on you for baksheesh.
In traffic circles in Nepal, if you're not wearing a helmet they will, no kidding, try to snatch the keys out of your ignition as you're passing by, or if they stop you. Protect your keys at all cost even if you have a helmet. It can be a hassle, unpleasant and cost you if they stop you, and if they get the keys it can get pricey.
They tried to snatch my keys once as I was riding but I was able to manuever away and kept going. I have met travellers who had worse luck. Also, I'm a woman so they're less inclined to hassle me.
Have a great trip!!!!
Yoga Hoolagan On an Enfield