Maybe try Moores Clothing for Men - they have a page for boy’s suit rentals, and have a few Ottawa locations. Might not be cheap, though.
Old Navy may have some…I just got my little guy a pair of navy pants that would pass muster as “dress” pants.
Question is whether they carry them across all sizes - he’s only 2.
Children’s Place would certainly carry some…at the right time of year. You might get lucky.
I second the suggestion for Moore’s. It’s the first place I’d look. Otherwise, Sear’s or The Bay - if not in the boy’s clothing section, see if there’s a boy’s size suit rack in the men’s suit section. I’d be really, really surprised if you couldn’t find something at one of these stores!
Is NO ONE here on the kid’s side?
He’s worked hard, he’s graduating, and you’re going to make him look like a dork? THAT’S the thanks he gets?
I just hope the poor kid doesn’t figure out that graduating=discomfort. He may just disappear a week before high school’s over.
ETA: I just saw that you yourself said: “I think dress clothes are falling out of fashion very quickly”… (there might just be a reason).
So why buy pants that’ll be worn only once? To make grandparents feel all warm and fuzzy at the child’s expense?
I apologize if you’ve asked the kid and he really wants dress pants.
I got my 13 year old some dress slacks at Target… but now that I think about it, that was about a week before Easter. So that may have been more of a seasonal thing, rather than a regularly stocked item.
I’m surprised you can’t find dressy slacks just about anywhere. But in terms of selling all the pieces of dressy wear for kids, when I was under 18 my Mom always took me to a department store, probably Sears but it could have been Macys.
The Bay should sell them or Sears boys department.
You can get overnight delivery from either of these:
No.
Even assuming you’re right and the kid wants to wear gym shorts, this is one of those “learning experiences” where he learns that there is such a thing as clothing appropriate to an event.
Otherwise he’ll be here in another 10 years in a panic because he’s never worn a suit and his girlfriend is begging him to wear one to a wedding and he has no idea what to shop for. Or in another 20 years, his wife will be posting a frustrated thread about why he won’t wear a suit to an event where it’s really important to her. 
Besides, lots of people, men included, really do enjoy dressing up once in a while. He won’t know if he’s one of those people if he’s never exposed to the option. You don’t learn how yummy asparagus can be if your parents always get you fries.
Found some. Thanks. We’re going to a mom and pop children’s clothing store this afternoon.
And digs, all the other boys will be dressed similarly, as they were when my daughter graduated grade 6 two years ago. They all like it!
If the derth of dressy pants isn’t a new thing, and if you strike out today, consider asking where either your son’s or daughter’s classmates bought their pants. Your daughter’s friends might not all remember, but surely someone will.