Yes, it's unfortunate that we can't travel on the COPR letter alone, given the long lag times for the actual card. If you absolutely cannot wait and need to travel without it, you have a apply for a Permanent Resident Travel Document (PRTD):
https://www.cic.gc.ca/english/helpcentre/answer.asp?qnum=064&top=10, which is a whole other application to fill out, submit, and pay. The PRTD assumes you're a PR that has lost their PR card abroad/while travelling outside of Canada, and there's no option or distinction for those who are travelling only before receiving the actual card.
And yes, I will let you know when I receive my card, although you hopefully and probably will receive yours before me!