Buried Service Line

Purchased a new house in December, should be moving in about 2 weeks. Noticed a few signs that I may have a water leak in yard. Dug up the spot today, found the leak. Black plastic pipe (polyethylene I assume) coming from meter, meter is at sidewalk. Copper pipe entering home through foundation. Leak is where the 2 pipes are joined together. Both pipes are 7/8in O.D. A compression coupling was used and is leaking on the plastic side. I believe this was the original install and not a repair, seems to have been leaking for years.

I've had the water off for over a month now. Been doing a lot of work in the house but don't live there yet. House was built in 2006, located near St. Louis Missouri (Lake St. Louis).

My question is about the proper materials to fix this. I found another compression fitting of the same style (JMF 7/8 Compression Fitting) and says it can be used on copper and plastic, but the plastic pipe requires a brass insert to keep from crushing the pipe. I have not yet taken apart the leaking one to see if it has an insert in good shape to reuse, may check tomorrow after work. Is there a better fitting to use? Where do these larger inserts come from? I have no problem finding smaller ones. Is there another piece of material not made for this that is an acceptable substitute? Any other advice?

Thanks.