His solution would be to apply for a PR travel document, see
http://www.cic.gc.ca/english/information/applications/travel.asp and once he is back in Canada, he can apply for a new PR card. If he is visa exempt to go to Canada, he can also try it without getting a travel document if he has his landing papers.
A PR can be outside Canada for up to 3 out of 5 years so he needs to do this before he loses his PR due to lack of residency. Time spent outside Canada with a Canadian spouse actually counts as time spent in Canada for those purposes but I am assuming his ex-wife will not back him up on that.