Keep looking, they're out there. Sometimes you have to contact 10-20 dealers to find what you need~just part of the game. 17M2s show-up in the EE from time to time as well, so keep your eyes open.
HMR is better-known, ammo/guns more readily available, but based on some "industry" types I've talked to, there is still a big demand for M2 ammo...so no plans to discontinue it. I have about 12 boxes of Hornady I'm not touching until I know I see ammo on the shelf locally again. I hear that shouldn't be too long.
Stick with it though~17M2 is a great little round. I've had 3 HMRs. They're gone, the M2 is still here.