As you already know that will be a difficult task, but not entirely impossible. Kentile Colonial Brick was a premium line that virtually every floor covering store would special order as it was sold. Only a few high-end retailers stocked it. So it's unlikely to find it as old stock at stores. Of course it's been discontinued and Kentile out of biz many years ago too.
However I think if you don't mind used replacements, I think there's a way. You should visit a high-end floor covering store that does installations and ask the sales staff to keep an eye for someone with that floor who is having it replaced with new. Offer to pay for the old tiles (which are worth big bucks) and offer a spiff too. Might work if you've got the time.
TILE GUY - retired- TROY, MI - Method & Product suitability consulting.