Doubt you will find anyone renting an R15 or 200NS. You will likely get a Pulsar if you look around hard enough. Also keep in mind that this is sort of off season, so hopefully you can bargain hard.
Renters with best rapport are Lali Singh and Bulletwallahs, but they mostly deal with foreigners and have Bullets and also charge a slight premium. Since you are going to arrive late, best option would be to talk to one of these guys and book in advance or schedule a day specifically for this purpose.
None of the renters provide riding gear, in fact some don't even provide basic tools and spares, so make sure you are getting those with whatever bike you rent.
There are also motorcycle renters in Rishikesh (as far as I know), but no idea about their quality.
Having said all this, my suggestion would be to ship your own motorcycle to Delhi and ride it. It will likely cost you around 500-600 bucks more if you do this, but you will have peace of mind and won't have to pay a deposit of 20-30k or more.