I bought a new water softener with 1" inlet/outlet tubing. The inlet/outlets are made of a hard, dark gray plastic that does not appear to be PVC, but, judging from the installation instructions, is sized to fit and connect to PVC connectors. I need to adapt this to connect to either pex or cpvc (I plan to use shark bite fittings from there). Souix Chief makes a push-on PVC to PEX adapter, but, apparently, no one actually sells it and e-mails to Souix Chief are unanswered. Any idea where I can but a 1" PVC to CPVC adapter, or PVC to CPVC adapter ? If not, what are my options?

The "gray plastic" is Schedule 80 PVC. Go to professional plumbing supply house, like Ferguson Enterprises to purchase your fittings or buy it on-line from places like CPVC plumbing products. I don't think Sioux Chief will send you fittings directly since they are the manufacturer. You will have to buy it from one of their distributors.

If you plan on using sharkbites, I would suggest going to a pluming store, or a big box store, and try to find a 1" MIP x 1" sharkbite fitting. (MIP=male iron pipe). This way you just teflon the male threads and thread it into the female threads on the softner. Then you can get a 1x3/4 sharkbite reducer if needed. Then just slide you pex into the sharkbite and your done. Don't forget to use the plastic insert sleeves if using pex.