Yes you can pull it without pulling the engine, and you can get the OEM part from any one of the OEM parts supplies, such as Rocky mountain ATV, Partzilla, etc. However, since you broke it once, you might has well upgrade the chain to an after market double chain, like Super ATV or Highlifter sells, while you're at it so you don't have the problem again.
I pulled my reverse chain with 50 miles on my car to upgrade. If you want it, you can have it. However, I highly recommend you do the upgrade. Pulling that trans is no small task and if you are going to spend the time, you might as well fix the issue